
fJass 3T"9T3 
Book ^M^_ 



CQPXRIGHT DEPOSIT. 



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HOG CHOLERA 



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THE MACMILLAN COMPANY 

NEW YORK • BOSTON • CHICAGO • DALLAS 
ATLANTA • SAN FRANCISCO 

MACMILLAN & CO.. Limited 

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THE MACMILLAN CO. OF CANADA, Ltd. 

TORONTO 



HOG CHOLERA 

ITS 

NATURE AND CONTROL 



BY 

RAYMOND R. BIRCH, B.S., D.V.M., Ph.D. 

PROFESSOR IN CHARGE OF THE NEW YORK STATE VETERINARY 
COLLEGE EXPERIMENT STATION AT CORNELL 
UNIVTERSITY, ITHACA, NEW YORK 



THE MACMILLAN COMPANY 
1922 

All rights reserved 



PRINTED IN THE UNITED STATES OF AMERICA 






^ 



Copyright, 1922, 
By the MACMILLAN COMPANY. 



Set up and printed. Published September, 1922. 



(y)CI.A681947 



Press of 

J. J. Little & Ives Company 

New York, U. S. A. 



SfP 21 1922 



PREFACE 

My object in preparing this book has been to place 
in the hands of those who handle hog cholera definite 
and authoritative information regarding the disease. 
There are abundant publications dealing with hog 
cholera but for the most part they consist of technical 
papers covering certain restricted phases of the disease, 
or of attempts to circumscribe the entire subject in the 
scope of a few pages. Neither meets the needs of the 
man who must handle hog cholera in the field. More- 
over these publications appear as bulletins or as special 
papers in technical journals, and usually they are not 
at the veterinarian's command at the time he needs 
them. 

We are rapidly discarding the old belief that any one 
who can use a hypodermic syringe can cope with hog 
cholera. Questions constantly arise regarding diagnosis, 
complications, when or whether to immunize, which 
method to use, the subsequent care of the herd, the 
handling of young pigs, slaughtering from infected 
herds under inspection, and many other individual prob- 
lems. 

The effective handling of hog cholera, like the handling 
of other diseases, is founded on exact knowledge of the 
malady itself, but hog cholera differs from other in- 
fectious diseases in that preventive vaccination against 
it has served to open the new field of swine practice. 



VI PKEFACE 

The result is that there are many veterinarians who 
will not attempt to cope with the disease, or who, 
making the attempt, feel the need for guidance. 

This volume is in no sense a compilation. For the 
most part it reflects personal experiences gained during 
ten years of intimate contact with hog cholera in the 
capacity of practicing and consulting veterinarian, anti- 
hog-cholera serum producer and research worker, but 
acknowledgment is due many other members of the 
veterinary profession whose researches and observations 
have revealed many of the foundation facts on which the 
subject matter rests. For statistical and other data I 
have consulted other authors freely, relying for sta- 
tistics especially on the numerous and excellent publi- 
cations of the United States Bureau of Animal Industry. 
I am indebted to Dr. E. A. Cahill, Director of the Pit- 
man-Moore Biological Laboratories, Zionsville, Indiana, 
for some of the illustrations. 

Dr. y. A. Moore, Dean of the New York State Veteri- 
nary College at Cornell University, and Dr. J. W. Benner 
of the College Experiment Station Staff have read the 
manuscript, and each has offered many valuable sug- 
gestions which are deeply appreciated. 

Great care has been taken to make the book a conserva- 
tive and accurate guide for the practicing veterinarian 
who must accept farm conditions as he finds them and 
handle hog cholera so as to secure and retain the con- 
fidence of his clients. If among other imperfections 
there are departures from this ideal I trust that my 
readers will direct my attention to them. 

R. R. B. 



CONTENTS 

CHAPTER PAGE 

I History and Economic Importance .... 1 

II Nature and Cause of Hog Cholera .... 7 

III Methods of Dissemination 17 

IV Complications 21 

V Symptoms and Lesions 35 

VI Diagnosis, Differential Diagnosis, Prognosis 58 

VII Preparation of Anti-hog-cholera Serum and 

Hog Cholera Virus 76 

VIII Methods of Using Anti-hog-cholera Serum . 118 

IX Handling Hog Cholera in the Field . . . 158 

X Hog Cholera, Meat Inspection and Garbage 

Feeding 197 

XI Control and Eradication of Hog Cholera . 230 



ILLUSTRATIONS 



PAGE 



1. Shoats affected with acute hog cholera 37 

2. Lung of pig showing eeehymoses due to acute hog 

cholera 46 

3. Left auricle of pig's heart showing peteehiae due to 

acute hog cholera 48 

4. Spleens showing hemorrhages which are rather typ- 

ical of acute hog cholera 49 

5. Kidney of pig showing numerous peteehiae due to 

acute hog cholera 51 

6. Lymph glands of pig showing hemorrhages caused 

by acute hog cholera 54 

7. Bleeding room in anti-hog-cholera serum laboratory. 

(Courtesy Pitman-Moore Biological Laboratories) 77 

8. Corner of anti-hog-cholera serum laboratory. New 

York State Veterinary College at Cornell Uni- 
versity 79 

9. Post-mortem room where autopsies on virus pigs 

are held 88 

10. A close view showing the hypering process ... 91 

11. Bleeding unit, and hog prepared for bleeding . . 99 

12. Bleeding for serum 101 

13. Testing anti-hog-cholera serum 107 

14. Injecting anti-hog-cholera serum in the ham . . . 119 

ix 



ILLUSTKATIONS 



PAGE 



15. Method of holding shoat for injecting serum in 

axillary space 120 

16. An improvised method of holding shoats for immun- 

izing 121 

17. Convenient hog holder made from ^/2 inch gas pipe, 

and flexible clothes wire 123 

18. Method of preparing snout rope for confining large 

hogs 124 

19. Method of noosing the snout of hog 125 

20. Injecting serum behind the ear 129 



HOG CHOLERA 

CHAPTER I 

HISTORY AND ECONOMIC IMPORTANCE 

Hog cholera seems to have appeared first on 
American soil in 1833, at which time an outbreak 
of the disease was reported in the Ohio valley. 
It is not definitely known whether the malady orig- 
inated in this country or in Europe, but it is 
a rather significant fact that the wild hog has 
flourished in Eurasia, and not in North America, 
in spite of the fact that the fauna of the two 
continents are in most other respects very closely 
related. It is also of special significance that the 
earliest authentic report we have of the disease 
in this country was made at a time when railroads 
were first being put into operation. It is there- 
fore possible that it really existed in America 
prior to that time, and that lack of facilities for 
its rapid spread prevented it from assuming the 
proportions of an epizootic. 

It is true that as early as 1822 an epizootic dis- 
ease resembling hog cholera was reported in 



2 HOG CHOLEEA 

France, and there is evidence that prior to 1833 
outbreaks of a similar nature occurred in other 
parts of continental Europe. But even with pres- 
ent-day knowledge hog cholera and other infec- 
tious swine diseases are sometimes difficult to 
differentiate, and we are thus in the dark relative 
to the true causes of all the earlier outbreaks. 

According to the most authentic records, hog 
cholera appeared in England in 1862, and from 
there, in 1887, it was carried to Sweden in a ship- 
ment of boars. In this same year the disease ap- 
peared in France and Denmark, and its spread 
was so rapid and persistent that all European 
countries have suffered severely from its ravages. 
To-day, no large area devoted extensively to swine 
raising is entirely free from hog cholera, and so 
far as we have been able to ascertain, no country, 
once invaded, has succeeded in freeing itself of 
the malady. The Scandinavian countries seem to 
have suffered least from its effects. 

Because of its rapid spread and high mor- 
tality hog cholera has caused and is causing enor- 
mous losses, the estimate being that in the United 
States it is responsible for ninety per cent of the 
deaths from all swine diseases. In this country 
the annual losses caused by it during the last four 
decades have ranged between $13,000,000 and 
$200,000,000, and in the two decades ending "with 
the year 1914 the average annual loss per one 



HISTORY AND ECONOMIC IMPORTANCE 6 

thousand hogs has been approximately 66. In 
1897, the loss per thousand ran as high as 130. 
Since 1914, the losses due to the disease have been 
gradually diminishing, and it is believed that more 
effective sanitary measures and more extensive 
and judicious use of protective serum have been 
responsible for this decline. 

Naturally a disease of such great economic im- 
portance has been the object of close and pro- 
longed study. In 1875, Dr. James Law furnished 
the United States Department of Agriculture with 
a report setting forth accurately the symptoms 
and lesions of the disease, and speaking for its 
transmissibility. Three years later, as a member 
of a commission of nine men appointed by the De- 
partment to investigate the disease, he succeeded 
in transmitting it by inoculation experiments. Dr. 
Detmers, acting as a member of the same commis- 
sion, isolated an organism which he regarded as 
its cause, but his findings were not confirmed. 

In 1885, Dr. Daniel Elmer Salmon and Dr. Theo- 
bald Smith isolated an organism, now kno^vn as B, 
suipestifer, which they believed to be the true 
cause of hog cholera. Their work was confirmed 
by trained investigators in this country and Eu- 
rope, but all attempts to produce immunity to 
field outbreaks by using B. suipestifer as an im- 
munizing agent ended in failure. Thus during 
the late nineties considerable doubt had developed 



4 HOG CHOLERA 

among some scientists relative to the true signifi- 
cance of this organism in its relation to epizootic 
hog cholera. This doubt was aroused because 
hogs that sickened as a result of injections of B, 
siiipestifer cultures failed to transmit disease to 
checks, because those that survived injection with 
cultures of the organism were not immune when 
exposed in field outbreaks, and because these cul- 
tures did not always produce disease, while blood 
from hogs sick as a result of natural infection 
proved to be quite generally infectious. In 1903, 
de Schweinitz and Dorset of the United States 
Bureau of Animal Industry demonstrated that the 
true cause of epizootic hog cholera is a filterable 
virus, and this marked an epoch in the history of 
the disease. 

Proceeding in the light of this new knowledge, 
Dorset, Niles and McBryde succeeded, in 1908, in 
adapting to hog cholera the principles employed 
by Kolle and Turner, NicoUe and Adil-Bey in pro- 
ducing a protective serum against rinderpest, a 
disease of cattle caused by a filterable virus. 
The work of Dorset and his associates was con- 
firmed by numerous investigators, among whom 
were Uhlenhuth, Hutyra and Xylander, and the 
epochal field experiments conducted in this coun- 
try by Dr. Niles and described by him in the re- 
port of the United States Bureau of Animal In- 
dustry, 1908, fully established the great practical 



HISTORY AND ECONOMIC IMPORTANCE O 

usefulness of anti-hog-cholera serum in checking 
the inroads of hog cholera in the field. 

Since 1908, rapid advances have been made in 
providing for an adequate supply of serum, in 
refining it, in working out methods for its use in 
the field, and in regulating its production so as to 
prevent sale of that which is contaminated or im- 
potent. All important hog-raising states in the 
Union have made provision to manufacture serum, 
and scores of private laboratories which have 
been established are being operated under super- 
vision of the Bureau of Animal Industry. In the 
refinement of the serum the aim has been to pro- 
duce, at low cost, a clear, sterile, potent product 
with good keeping qualities. This ideal is rapidly 
being attained, but there are still serious questions 
regarding uniform potency and keeping qualities 
of the clear serum, and the equipment required in 
making it is rather crude, and cannot be said to 
have passed the developmental stage. 

Finally, it should be related that with the 
knowledge that hog cholera can be controlled, 
there has appeared a quickened interest in all 
other maladies that affect swine, especially those 
frequently complicated with hog cholera. Undue 
importance has sometimes been attached to some 
of these diseases, and such extravagant claims 
have been made for certain biologies used as pro- 
phylactic or therapeutic agents that there has 



6 HOG CHOLERA 

been a sharp reaction, and there are indications 
at present that the trend of opinion may even 
swing too far in the opposite direction. The dis- 
eases that complicate hog cholera present very 
real problems, and experimental work looking to- 
ward a deeper understanding of them is one of the 
immediate needs of the present day. 



I 



CHAPTER II 

NATURE AND CAUSE OF HOG CHOLERA 

Hog cholera is an acute, communicable, febrile 
disease which attacks swine of all breeds and ages, 
but does not afPect other domesticated animals, or 
man. It is a septicemia. Occasionally a per- 
acute form of the disease is recognized during the 
first days of an outbreak and chronic hog cholera 
is frequently observed among the stragglers that 
survive the more severe and rapidly terminating 
forms. In the individual, the disease is charac- 
terized by sudden onset, inappetence, chilling^ 
very high fever, arched back, a disposition to hide 
in the litter, constipation followed by diarrhea, 
general weakness in the later stages, accompanied 
by purplish discolorations of the skin covering the 
belly, ears and snout. In the herd, the onset is 
relatively slow, the first death usually preceding 
subsequent ones several days, but after the first 
week the outbreak rapidly gains momentum, and 
in a comparatively short time all hogs become in- 
fected. The mortality ranges between 80 and 100 
per cent with a strong tendency to approach the 

latter figure. 

7 



8 HOG CHOLEEA 

Young pigs, especially those farrowed and 
nursed by immune mothers, are often immune to 
cholera during the first few weeks of life, and a 
general impression that all pigs nursing immune 
sows are likewise immune seems to have gained 
ground. This impression is not in accord Avith 
the facts, for we have seen individual pigs born of 
immune mothers and suckled by them, dead of 
hog cholera on the seventh day following birth, 
and under like conditions of birth and sustenance 
we have frequently seen entire litters succumb to 
the disease before attaining an age of four weeks. 
Among older hogs raised in localities where hog 
cholera is not prevalent, the ^'natural immunes'' 
so frequently mentioned are by no means common, 
and it is probable that in places where they are 
found in considerable numbers they owe their im- 
munity to the fact that they are exposed to cholera 
as young pigs, and suffering only a slight reac- 
tion, are rendered immune. As a general rule, 
young shoats, old hogs, and sucking pigs are most 
susceptible to cholera in the order named, and, as 
would be expected, recoveries from the disease 
are less frequent among young shoats, and more 
frequent among old sows and sucking pigs. 

The cause of hog cholera is a filterable virus, 
probably an organism too small to be visible with 
the highest magnification now obtainable, and pos- 
sibly possessed of characteristics which prevent it 



NATURE AND CAUSE OF HOG CHOLERA \) 

from taking stains that render bacteria more 
plainly visible. The virus readily passes porce- 
lain and infusorial earth filters which retain all 
visible bacteria, but it is itself retained by the 
finest porcelain filters. It does not pass through 
colloid membranes. In the human subject, mea- 
sles, mumps, scarlet fever and smallpox are among 
the diseases caused by filterable viruses, while 
among animals rinderpest, foot-and-mouth dis- 
ease and rabies are some of the diseases that fall 
in the same group. The classification is a rather 
loose one, being based entirely on the fact that 
these viruses will pass filters that retain visible 
bacteria, rather than on morphological or cultural 
characteristics. 

There is no conclusive evidence that hog cholera 
virus has been propagated outside the bodies of 
infected swine. After a hog has been exposed to 
the disease and actually infected, the virus ap- 
pears in the blood stream in about four days, and 
thus all vascular organs harbor it during the at- 
tack. In the later stages of a few chronic cases, 
we have found the blood free of the virus, but we 
do not know whether this is the rule, nor is there 
definite knowledge of the part played by '^ car- 
riers'' in harboring it. It is eliminated through 
the excretions. The urine is regularly infectious, 
the feces may or may not contain it, and the dis- 
charge from the eyes and skin ulcers is infectious 



10 HOG CHOLERA 

at least in some instances. Just how any one of 
the filterable viruses operates to produce disease 
is quite unknowm, but it is certain that hog cholera 
virus has a selective action for epithelial and en- 
dothelial cells. 

Virulence. Hog cholera virus produces speci- 
fic disease only in swine, and very small quantities 
of infected material are sufficient to cause death 
in susceptible animals. According to King, sub- 
cutaneous injections of 1/86 of a mil of virulent 
blood produced the disease, while lesser amounts 
produced only a mild reaction, or none at all. 
Natural infection usually occurs by way of the 
digestive system, but the disease is readily pro- 
duced by subcutaneous, intravenous or intra-abdo- 
minal injections of small quantities of virulent 
material. 

Resistance. Most of the natural influences to 
which hog cholera virus is subjected do not oper- 
ate to destroy it rapidly. Drying, sunlight, and 
low temperatures seem to have no immediate at- 
tenuating effects, although it is a fact that most 
infected yards which remain uninhabited from 
three to six months do not endanger susceptible 
pigs placed in them. There is, though, a consid- 
erable tendency for hog cholera to recur on old 
infected farms, and this fact indicates that there 
are exceptional cases in which the span of life 
of the virus is greatly prolonged. 



NATURE AND CAUSE OF HOG CHOLERA 



11 



Putrefaction is the only natural influence 
which operates to destroy the virus rapidly. Ac- 
cording to Uhlenhuth it will live in putrefying car- 
casses for about eight days, but undoubtedly the 
many influences which govern putrefactive proc- 
esses render data of this kind of value merely in 
establishing tendencies. It is certain that decom- 
posing carcasses do not harbor the virus regu- 
larly, and likewise it is true that virus kept in bot- 
tles in the laboratory often is killed when putre- 
faction develops. When sufficient preservative is 
added to prevent the growth of putrefactive or- 
ganisms, the virus regularly lives several months, 
and may even exist for years. 

Moderate degrees of heat attenuate or destroy 
the virus, and under no circumstances has it been 
found to survive temperatures near the boiling 
point. The following rather incomplete table pre- 
pared by the German Imperial Board of Health 
laboratories gives a fair idea of the effects pro- 
duced by various degrees of heat. 



Degrees 
Material Centigrade Time 

Liquid serum 
filtrate 45 24 hours 

Liquid serum 

filtrate 46.5 24 hours 



Results 

Not killed or 
weakened 

Not killed or 
weakened 



12 


HOG 


CHOLERA 




Degrees 
Material Centigrade 


Time 


Results 


Liquid serum 
filtrate 


46 


48 hours 


Killed 


Liquid serum 
filtrate 


55 


24 hours 


Killed 


Liquid serum 
filtrate 


60 


10 hours 


Killed 


Liquid serum 
filtrate 


58 


2 hours 


Not killed 


Liquid serum 
filtrate 


78 


1 hour 


Killed 


Dried blood 


65 


2 hours 


Not killed 


Dried blood 


72 


1 hour 


Killed 


Dried blood 


72 


1/2 hour 


Killed 


Urine 


58 


1 hour 


Killed 


Urine 


58 


% hour 


Not killed 



Low temperatures act to prevent growth of 
putrefactive organisms and are thus instrumental 
in prolonging the life of the virus. In our oami 
experiments, hams removed from cholera infected 
pigs and frozen hard ninety-three days still har- 
bored virus sufficient to produce the disease when 
small portions of them Avere fed to susceptible 
pigs. 

Disinfectants. Hog cholera virus readily re- 
sists ordinary disinfectants in dilutions that are 
rapidly fatal to most bacteria. When % per cent 
phenol is added to virulent blood, the virus mil 
remain alive for months, and all of the coal tar 
disinfectants must be prepared in strong solutions 
in order to destroy it. Liquor cresolis compositus 



NATURE AND CAUSE OF HOG CHOLERA 



13 



in 5 per cent aqueous solution, when allowed to act 
for an hour or more, has proved effective in killing 
it. Following is a table prepared by the German 
Imperial Board of Health laboratories, which fur- 
nishes additional information relative to the efP ec- 
tiveness of various disinfectants when used to kill 
hog cholera virus. Most of the tests were made 
by mixing 10 mils of the virus with an equal 
quantity of aqueous dilution of the disinfectant. 

Dilution 

applied Result 



Disinfectant 

Corrosive 

sublimate 

Corrosive 
sublimate 

Corrosive 
sublimate 



Carbolic 
acid 

Carbolic 
acid 

Carbolic 
acid 

Carbolic 
acid 



0.3 per cent solution Serum filtrate not 

killed in 8 days. 

0.5 per cent solution Serum filtrate virus 

not killed in 4 days. 

0.2 per cent solution Urine virus killed 

in 15 minutes in 
one trial. In another 
trial not killed. 

0.5 per cent solution Serum filtrate virus 

not killed in 8 days. 

1.0 per cent solution Serum filtrate virus 

not killed in 4 days. 

3.0 per cent solution Failed to kill blood 

virus in 8 days. 

2.5 per cent solution Failed to kill urine 

virus in 15 minutes. 



14 



HOG CHOLERA 



Dilution 
Disinfectant applied 

Chloroform Full strength 



Sodium 
taurocholate 

Formaldehyd 2.5 per cent solution 



Lugol 's 
solution 



Urea 



0.25 per cent solution 



20.0 per cent solution 



Glycerin 33.0 per cent solution 



Ozone 



Hydrogen 

peroxid 10.0 per cent solution 

Antiformin 5.0 per cent solution 

Antiformin 2.0 per cent solution 



Result 
Serum filtrate virus 
not killed in 24 
hours. 

Blood virus not 
killed in 4 days. 

Serum filtrate virus 
alive after one hour. 
Dead in 15 days. 

Failed to kill serum 

filtrate virus in 2 

hours. 

Did not kill serum 

filtrate virus in 1 

month. 

Failed to kill serum 
filtrate virus in 1 
month. 

Blood virus not 
killed. 

Serum virus not 
killed in two hours. 

Serum filtrate virus 
killed in one hour. 
Urine virus not 
killed in 10 minutes. 
Killed in 15 min- 
utes. 



Antiformin 1.0 per cent solution Serum filtrate virus 

not killed in 24 
hours. 



NATURE AND CAUSE OF HOG CHOLERA 



15 



Disinfectant 
Antiformin 



Milk of lime 



Chlorid 
of lime 



Lysol 



Dilution 

applied Result 

2.5 per cent solution Serum filtrate virus 

killed in 2 hours. 
Blood virus not 
killed in two hours. 

Failed to kill in one 

hour. In other ex- 
periments killed in 
20 min. 



5.0 per cent solution 
3.0 per cent solution 



Serum virus killed 
in 114 hours. 
Serum filtrate virus 
usually killed in 1 
hour. 



Cresol soap 

solution 3 — 6 per cent solution Always killed virus 

in 1 hour. 
Cresol soap 
solution 3 — 4 per cent solution Serum filtrate virus 

not killed in % 

hour. 
Cresol soap 
solution 3.0 per cent solution Killed urine virus 



m 



hour. 



Since a filterable virus has been incriminated as 
the true cause of hog cholera, various investiga- 
tors have from time to time attempted to isolate it, 
stain it, and grow it on artificial culture media. 
King has made an exceedingly careful study of a 
spirochaete (Spirochaeta hyos) which to him has 
seemed to possess etiological significance, but his 



16 HOG CHOLERA 

work has never been verified. More recently 
Proescher and Sell have described a diplococcus 
which they are inclined to regard as the virus of 
hog cholera, but as yet they have not submitted 
substantial proof to justify such a claim. Certain 
cell inclusions which in cholera-infected hogs ap- 
pear in the epithelial cells of the conjunctival sac 
have also been regarded as possible possessors of 
pathogenic powers, but it now seems probable that 
these exist as an effect rather than as a cause. 
There are various organisms which, acting as 
secondary invaders, exert profound influence on 
the course of hog cholera and on the lesions which 
develop, but which should in no way be confused 
with the filterable virus that produces the dis- 
ease. These will be considered in another chap- 
ter. 



CHAPTER III 

METHODS OF DISSEMINATIOIT 

Hog cholera virus exists only in infected hogs 
and in material contaminated by their excretions, 
and this is the fundamental fact to which we must 
repeatedly refer in accounting for new outbreaks. 
There are numerous exceptions to the rule, but 
the individual outbreak can usually be traced to 
a definite source, and this fact is important in its 
relation to measures for control. 

Shipping infected animals is probably the one 
practice responsible for most new herd infections. 
It is not uncommon for a breeder to become dis- 
couraged when his hogs begin to die and to ship 
all seemingly well animals to a distant market. 
During the fall of the year especially one has but 
to stand for a few hours at the unloading chutes 
of some of our large stockyards in order to realize 
how nearly universal this practice has become. 
Thus most public stockyards harbor hog cholera 
virus, and all hogs unloaded in them and later 
taken to farms for feeding or breeding become 
potential sources of danger. 

In the eastern states garbage feeding is re- 
sponsible for more outbreaks of hog cholera than 

17 



18 HOG CHOLERA 

all other factors combined, and in the country 
as a whole this practice plays an exceedingly im- 
portant part in the spread of the virus from local- 
ity to locality. Many hogs are killed while they 
are in the incubation period of cholera, and pork 
that comes from their carcasses, even though it is 
fit for human food, will produce hog cholera when 
fed in small portions to hogs. Bits of this in- 
fected pork find their way into garbage which is 
fed to susceptible swine, and the cycle is com- 
plete. 

The use of hog cholera virus in the field in 
serum- virus immunization has now become a rou- 
tine measure, and despite the advantages that re- 
sult from this practice, it must in truth be said 
that it is responsible for many new outbreaks of 
hog cholera. The practice of giving feeding 
shoats serum-virus treatment and shipping them 
immediately to distant points operates to infect 
much new territory, and is often the cause of 
heavy losses among the hogs thus handled. 
^^Vaccination cholera," as these ^ ^breaks" follow- 
ing serum-virus treatment are called, although it 
usually runs a less rapid course which invites sec- 
ondary infection, is not fundamentally different 
from hog cholera contracted as a result of natural 
infection, but there is a marked tendency in some 
quarters to avoid the issue and attribute the 
deaths to causes other than hog cholera virus. 



METHODS OF DISSEMINATION 19 

The practice of taking breeding hogs to dis- 
tant points to mate them is a fruitful source of 
new herd infections, and in more than one instance 
we have known the virus to be carried from one 
farm to another as a result of neighbors exchang- 
ing help during butchering time. Small streams 
to which many hogs have access may also become 
polluted and carry destruction to herds below the 
one in which the original infection occurs. Show 
hogs returned from fairs often contract hog chol- 
era en route or during their contact with other 
hogs in the show ring, only to infect the herds they 
represent when they return home. 

Besides the regular channels of infection which 
we have already indicated, and which severally 
are responsible for most new outbreaks of hog 
cholera, there are almost an infinite number of 
casual carriers of the virus, such as crows, spar- 
rows, buzzards, pigeons, and various predatory 
animals. These, by feeding in infected yards or 
on carcasses of hogs dead of cholera, may carry 
the infection to clean territory, but the probabili- 
ties are that in most localities the number of herds 
thus infected is relatively small. 

In recent experiments Dr. Marion Dorset has 
found it difficult to transmit hog cholera from 
herd to herd by employing attendants, pigeons 
and sparrows as agents of transmission, and in 
our own experiments we have failed in a surpris- 



20 HOG CHOLEKA 

ing percentage of cases to infect yards with hogs 
sick of cholera so that susceptibles placed in them 
subsequently will contract the disease. In spite 
of these facts, though, we must in handling hog 
cholera be guided by the practically universal 
clinical experience which teaches that when hog 
cholera once finds its way into a farm herd it will 
eventually infect all individuals in it, irrespective 
of the fact that the herd may consist of several 
pens of hogs kept some distance apart. 

It is impossible, and indeed unnecessary, to dis- 
cuss in detail the various influences which occa- 
sionally are instrumental in carrying hog cholera 
virus from herd to herd, and like^\ise it is impos- 
sible to assign to each influence a relative import- 
ance. It is much more important, in concluding 
this chapter, to call attention again to the fact 
that in the great majority of cases hog cholera 
virus travels in certain quite definite channels, and 
that new outbreaks are usuall}^ the direct or in- 
direct result of shipping or moving infected hogs, 
or else they originate from the practice of garbage 
feeding, or that of using hog cholera virus indis- 
criminately in seeking to immunize against the 
disease. 



CHAPTER IV 

COMPLICATIONS 

Before we consider the symptoms, lesions and 
diagnosis of hog cholera, it is necessary that we 
shall discuss briefly some of the organisms that 
complicate the disease, and which at times exert 
such profound influence on its course that autop- 
sies become a continual source of surprise and 
perplexity to the diagnostician. No attempt will 
be made to give complete morphological and cul- 
tural characteristics of these organisms, which in- 
formation may be found in various standard 
works on bacteriology. The scope and purpose 
of this book require that we shall deal only in a 
general way with most biological characteristics, 
confining our attention chiefly to disease produc- 
ing power, especially in swine. 

Bact. suisepticum is the most important of the 
organisms that complicate hog cholera. It was 
isolated and described by Loeffler and Schiitz in 
1885, and in 1886 Dr. Theobald Smith recovered 
it from various organs of many hogs dead of an 
epizootic disease in this country. Moore showed 
that it is present in the upper air passages of 

21 



22 HOG CHOLERA 

many healthy swine. In the absence of knowledge 
of the filterable hog cholera virus, all these investi- 
gators were inclined to regard the organism as the 
cause of epizootic swine plague, and to ascribe 
repeated failures in causing it to produce trans- 
missible disease, to the fact that field conditions 
could not be duplicated in the laboratory. 

The organism is rod-shaped varying in length 
from .8 to 2 microns, and in width from .4 to 1.2 
microns. Often the ends are rounded giving it 
an oval shape, but it is not uncommon for the rods 
to be so short as to resemble micrococci. Some- 
times involution forms are observed. In cover- 
glass preparations made direct from the tissues 
and stained with basic aniline dyes, Bact. suisepti- 
cum often stains heavily at the ends and around 
the periphery, and very lightly or not at all in the 
center. Preparations made from cultures do not 
as a rule exhibit this bipolar staining. 

The organism is subject to wide variation in 
virulence. Rabbits, mice and guinea-pigs readily 
succumb to injections of minute quantities of cul- 
tures or suspensions containing it. Eabbits are 
especially susceptible, usually dying in less than 
thirty-six hours of an acute bacteremia. Like cul- 
tures or suspensions injected subcutaneously into 
cholera immune pigs produce as a rule a transient 
local reaction. Small doses injected intravenously 
may or may not prove fatal, but large intrave- 



COMPLICATIONS 23 

nous doses produce death from septicemia quite 
regularly. The pigs that die in less than seventy- 
two hours may show as lesions congestion of the 
lymph glands and various parenchymatous or- 
gans, or, more rarely, petechial hemorrhages in 
the kidneys and heart, indistinguishable from 
those observed in acute hog cholera. In the cases 
in which the disease runs a less rapid course, there 
is a rather constant tendency for joint lesions of 
an inflammatory nature to form, and, contrary to 
what might be expected, pleuritis and pneumonia 
appear much less frequently than these joint le- 
sions. Earely do checks kept with these experi- 
mental animals contract disease.^ 

The symptoms that appear in pigs artificially 
infected with large intravenous doses of Bact. 
suisepticum are observed in a very few hours 
after the injection. There is rapid breathing, 
sometimes an extreme degree of dyspnea, or the 
respiratory disturbance may manifest itself in 
^ ' thumping. ' ' The appetite is suspended, the tem- 
perature is moderately high (104°-105.5° F.) and 
there is an anxious facial expression. A general 
stiffness is practically always observed, and 



*In our own experiments, in which more than 100 pigs were 
exposed in pens with pigs artificially infected with intravenous 
injections of Bact. suisepticum, 3 contracted disease and 2 died. 
Bact. suisepticum was recovered from the blood and various 
parenchymatous organs of the dead animals. We know of no 
other well authenticated instances in which like transmission has 
occurred. 



24 HOG CHOLERA 

lachrymation often is pronounced. If death or 
recovery does not take place in two or three days, 
the tendency is for the disease to assume a chronic 
type. One or more of the joints, usually the knee 
or hock, becomes hot, painful, and swollen, render- 
ing it difficult or impossible for the animal to 
stand. In spite of this, the temperature falls and 
is maintained close to normal, the appetite returns 
and is surprisingly good considering the condition 
of the animal and the fact that progressive ema- 
ciation is taking place. Pneumonia sometimes 
appears in these chronic cases, adding its train of 
symptoms, but it fails to develop in a surprising 
percentage of cases, thus presenting a striking 
comparison with field outbreaks formerly thought 
to be caused solely by Bact. suisepticum, in 
which pneumonia is the most constant manifesta- 
tion. These facts lead us to doubt that the or- 
ganism, acting alone, is the cause of a rapidly 
transmissible disease in the field. 

Field observations are in almost perfect accord 
with these experimental data. We have frequently 
had outbreaks of ''pure swine plague" reported 
to us, and in those we have investigated, in which 
there was evidence of transmissible disease, we 
have without exception succeeded in positively 
demonstrating or establishing the probable pres- 
ence of the filterable hog cholera virus. It is also 
significant that in the East, at least, cholera im- 



COMPLICATIONS 25 

mune hogs do not suffer from *^ swine plague'^ if 
we except the cases in which it is said to appear 
in the first month subsequent to serum- virus treat- 
ment, and which in reality have their origin in 
the hog cholera virus used. 

Acting as a secondary invader in hogs suffering 
with cholera, in those badly infested with lung 
worms, and very probably as a primary microbian 
cause in those weakened as a result of shipping, 
Bact. suisepticum regularly produces a rather 
characteristic bronchopneumonia, and hastens or 
causes death. In those cases in which it acts as a 
secondary invader it produces pneumonia so rap- 
idly and regularly that the lesions due to the pri- 
mary cause are often obscured or overlooked. 
Cholera immune farm hogs kept in exceedingly 
bad sanitary surroundings and exposed regularly 
to damp and inclement weather, have not been 
shown to suffer from a rapidly transmissible and 
fatal pneumonia caused by this organism. There 
is, though, some experimental evidence that it oc- 
casionally produces pleuritis or possibly slight 
pneumonic lesions from which most hogs recover. 

B. suipestifer (B. cholerce suis) is another or- 
ganism which may often be isolated from various 
parenchymatous organs of hogs dead in outbreaks 
of cholera. It is a short, motile rod, belonging 
to the colon group. In 1885 it was described by 
Salmon and Smith as the cause of epizootic hog 



26 HOG CHOLEEA 

cholera. In later years Uhlenhuth and his co- 
workers reported finding it in the intestinal tracts 
of many healthy smne. Jordon, in this country, 
was unable to identify it in any normal hogs which 
he examined, and neither Avas Tenbroeck. Both 
of these investigators regard Uhlenhuth 's work as 
inconclusive owing to the fact that he did not 
differentiate correctly between B. suipestifer and 
B. paratyphoid B. Smith states that the only dis- 
tinction that can be made between the two is that 
the former is pathogenic for rabbits, while the 
latter is not. 

Eabbits and guinea-pigs succumb to small sub- 
cutaneous injections of cultures of B. suipestifer, 
rabbits being somewhat more susceptible. Swine 
are not easily infected with subcutaneous injec- 
tions, but large intravenous doses prove fatal. 
According to Welch, small doses may lead to for- 
mation of the ^^ button ulcers" observed in chronic 
hog cholera, and Smith secured like results by 
feeding pigs bouillon cultures. 

The part played by this organism in producing 
swine disease in the field is not well defined, as 
most work with it ceased as soon as the filterable 
virus was accepted as the cause of epizootic hog 
cholera. There is good evidence that it is one 
cause of the ^'button ulcers'' just mentioned, and 
it is likemse probable that, acting in the role of 
secondary invader, it is responsible for the en- 



COMPLICATIONS 27 

larged, dark, and somewhat pulpy spleens ob- 
served in individual hogs dead in outbreaks of 
cholera. It also seems to intensify hemorrhagic 
lesions produced by the filterable virus. Its 
pathogenic powers in relation to cholera immune 
pigs will bear further investigation, but it is prob- 
able that for the most part it acts to complicate 
diseases produced by other causes. 

B. pyocyaneus, or, according to Migula's classi- 
fication, Pseudomonas pyocyaneus, is a motile rod 
2 to 6 microns long and .3 to 1 micron broad. It is 
widely distributed in nature, and there has been a 
tendency to regard it chiefly as a saprophyte. It 
is included frequently in the flora of wounds, it 
appears at times in abscesses in swine and other 
animals, and it has been described as the cause of 
an outbreak of dysentery in man. In Germany it 
is said to be the cause of an infectious nasal 
catarrh in pigs, and we have found it associated 
with outbreaks of pneumonia in swine, as the prob- 
able cause. 

The organism is an aerobe, it grows luxuriantly 
on the common culture media, tending to over- 
whelm other bacteria associated with it. It has a 
marked tendency to produce green color in any cul- 
ture medium, and the sweetish odor produced by 
it in bouillon cultures is quite characteristic. It 
takes the aniline stains regularly, and is Gram 
negative. 



28 HOG CHOLERA 

B. pyocyaneus is pathogenic for pigeons, guinea 
pigs and rabbits. In swine, it is not regularly so, 
but under certain conditions it assumes great 
pathogenic significance. We have failed to pro- 
duce disease by feeding cultures of it or by spray- 
ing them into the nostrils of healthy pigs, while 
subcutaneous doses produced nothing more than 
an occasional local abscess. Moderate intrave- 
nous doses of suspensions containing it cause 
dyspnea, chilling or spasms to appear immedi- 
ately, and death, preceded by paralysis, usually of 
the hind quarters, often takes place in a day or 
two. This paralysis is observed in rabbits as well, 
and must be regarded as a more or less constant 
but nevertheless specific action on the part of the 
organism. According to Hutyra, cultures of B, 
pyocyaneus inoculated directly into the ethmoid 
mucosa in young pigs, produce disease similar to 
the catarrhal rhinitis observed in Germany. 

Under natural conditions certain predisposing 
factors, among which early age, lung worms, hog 
cholera virus and long confinement in very dusty 
quarters are most important, prepare the ground 
so that J5. pyocyaneus exerts its pathogenic pow- 
ers. We have observed its effects following 
hyperimmunization during the process of anti-hog- 
cholera serum preparation, the hypers developing 
a fatal pneumonia in a few days following a large 
intravenous dose of hog cholera virus. 



COMPLICATIONS 29 

The lesions produced in swine experimentally 
infected by means of intravenous injections of 
material containing B. pyocyaneus are those char- 
acteristic of septicemia, congestion and dark col- 
oration of the lymph glands, lungs, kidneys and 
other organs appearing regularly. We have ob- 
served no such effects where natural infection 
rules. Here the constant lesion produced is pneu- 
monia, acute or chronic, and the constant symp- 
toms that appear are those that may be referred 
to this condition. 

Dyspnea, abdominal breathing and other 
marked evidence of respiratory distress charac- 
terize the disease. Paroxysms of coughing occur 
when the hog is required to move, the alae of the 
nostrils are drawn backward, giving the snout a 
peculiar pointed appearance, and it is not uncom- 
mon for the affected animals to assume a dog- 
sitting position, with the forelegs placed widely 
apart. Thumping appears frequently. Some- 
times there is a yellowish purulent discharge from 
the nostrils. The appetite may or may not be 
affected, while the temperature, as a rule, remains 
normal or is only slightly elevated. 

The typical lesion which we have found associ- 
ated with natural infection due to B. pyocyaneus 
consists of a semi-chronic type of bronchopneu- 
monia, affecting first the ventral and cephalic 
portions of the lungs, or if lung worms are pres- 



30 HOG CHOLERA 

ent, the posterior border of the diaphragmatic lobe 
as well. The solidified portions may be red but 
are often rather light in color, macroscopically 
resembling the surface of a salivary gland. There 
is a marked tendency for necrosis to develop 
from numerous foci, and multiple abscesses occur, 
appearing as slightly elevated yellow areas dotted 
over the surface of the pneumonic lung. Pleuritis 
is somewhat constant, and a high degree of em- 
physema appears in the dorsal nonpneumonic por- 
tion, giving it a pale white color as compared to 
the normal pink. Often there is distinct evidence 
that as a final cause of death an acute pneumonia 
is superimposed over a more chronic type, in 
which cases all parts of the lungs are pneumonic, 
while the lesions in the dorsal and posterior por- 
tions are of more recent origin. 

B. necrophonis is another organism that some- 
times complicates hog cholera. Although subject 
to wide variations in form, it usually appears as a 
long, slender, nonmotile rod. It is a strict anaer- 
obe, it stains with the ordinary aniline dyes, and 
is Gram negative. Evidently it is quite widely 
distributed in nature, for it appears in numerous 
necrotic lesions in practically all domesticated ani- 
mals. It is regarded as a normal inhabitant of the 
intestinal tract in swine, and it exists in soil con- 
taminated with manure. It is the exciting cause 
of calf diphtheria, lip and leg ulceration in sheep, 



COMPLICATIONS 31 

and a necrotic stomatitis of calves and pigs, each 
of which partakes somewhat of the nature of a 
specific infectious disease, but none of which, with 
the possible exception of calf diphtheria, tends to 
be reproduced regularly, in typical form, by arti- 
ficial means. 

In swine, B. necrophorus may be the. primary, 
and usually is the exciting cause of various ne- 
croses which appear in the mouth, stomach and 
intestines, nasal passages, skin, and lungs, and 
are designated, respectively, according to loca- 
tion, necrotic stomatitis, enteritis, rhinitis (bull 
nose), dermatitis and pulmonary bacillosis. The 
typical lesion consists of a dark brown necrotic 
patch which spreads slowly and tends to penetrate 
the deeper structures. Frequently a yellowish- 
broA\Ti scab or false membrane is formed. In ne- 
crotic stomatitis and enteritis especially, numer- 
ous lesions often coalesce until large areas are af- 
fected, and, depending on location, even the man- 
dible itself may be involved or the intestinal wall 
penetrated. A foul odor is usually detected. In 
the mouth, the lesions usually take origin from 
teething wounds or other slight abrasions ; in the 
stomach and intestines, hog cholera lesions and 
various irritants prepare the ground for their 
development; in the nasal passages they follow 
rhinitis due to other causes ; in the skin, they ap- 
pear especially on the teats and udders of sows 



32 HOG CHOLERA 

which are chapped or wounded as a result of nurs- 
ing litters. We know less regarding the primary 
cause of necrotic lesions that appear in the 
lungs. 

It is still an open question whether B. necropho- 
rus is really capable of penetrating normal mu- 
cous membrane and producing its characteristic 
effects, but usually it does not. Likewise there is 
doubt as to whether it releases a toxin, the prob- 
ability being that at times it does, for especially in 
young pigs suffering with necrotic stomatitis, 
death often takes place suddenly, before it can be 
explained on the basis of the existing local lesion. 
On the other hand, some pigs will harbor surpris- 
ingly extensive lesions without marked systemic 
disturbances. Some regard B. necrophorus as a 
secondary invader that may cause the * ^button 
ulcers'^ which appear in chronic hog cholera, but 
there is at least a distinct difference between the 
button ulcer in which degenerative and regenera- 
tive processes coexist, and the usual lesion pro- 
duced by B. necrophorus, in which a progressive 
necrosis prevails as long as the exciting cause re- 
mains active. There is also somewhat meager 
evidence that the organism may in rare instances 
cause petechial hemorrhages in the serous mem- 
branes and kidneys. 

Bad. suisepticum, B. sidpestifer, B. pyocya- 
neus, and Bad, necrophorus have two characteris- 



COMPLICATIONS 33 

tics in common. All are of a subvirulent nature, 
usually depending on other influences or predis- 
posing causes to enable them to exert their patho- 
genic powers, and all frequently take advantage 
of the lesions produced by hog cholera virus, in 
which they establish themselves, changing the 
course of the disease, and rendering autopsies 
puzzling and inconclusive. 

There are several other organisms that have 
been associated with hog cholera, either as com- 
plicating influences or probable causes, but some 
of these normally lead a saprophytic existence, 
and with our present knowledge we are unable to 
assign to any one of them a definite pathogenic 
role. B. coll communis and other members of the 
group, together with various streptococci and 
micrococci may often be found in lungs of hogs 
that have died of a terminal pneumonia brought 
on by hog cholera. Spirochceta hyos (King) is 
sometimes found in the blood and intestinal le- 
sions of hogs suffering with cholera, and B. py- 
ogenes suis is found in various suppurating lesions 
in swine, some of which have died in hog cholera 
outbreaks. The collective primary and secondary 
effects of all the organisms considered in this 
chapter, together with the changes produced by 
hog cholera virus go to make up the symptom- 
complex which, conveniently but unfortunately, 
has come to be known as ^^ mixed infection,'' and 



34 HOG CHOLERA 

handled as a single entity. Only when we begin 
to inquire more closely into the disease-producing 
powers of each organism will real progress be 
made. 



CHAPTER V 

SYMPTOMS AND LESIONS 

Following the subcutaneous injection of a 
small quantity of hog cholera virus, or the feeding 
of material containing it, symptoms of the disease 
usually appear between the fifth and eighth days. 
In herds through which the disease is spreading, 
several weeks are often required for it to reach 
all individuals, but this delay must be regarded 
as due to failure of some of the hogs to take up the 
virus, rather than as a prolonged incubation 
period. The incubation period usually given va- 
ries between four and twenty-one days, but in the 
vast majority of cases symptoms will appear in 
less than nine days following definite exposure 
(feeding or inoculation) of susceptible pigs. 

Three forms of hog cholera are recognized, per- 
acute, acute and chronic. The peracute form is 
relatively infrequent, but it occurs occasionally 
among the first few hogs that succumb in an out- 
break. No definite symptoms have been asso- 
ciated with this form of the disease, for the af- 
fected animals are found dead with no history of 

previous sickness. 

35 



36 HOG CHOLEKA 

The acute form, which includes the great ma- 
jority of cases, begins with high fever (105°-109° 
F.), arched back, chilling, rough coat, drooping 
ears and tail, and general depression. The appe- 
tite is impaired. The affected animals may crowd 
to the trough in the usual greedy fashion, but 
after drinking sparingly of any liquid that may be 
contained in the feed, they return languidly to 
the nest in advance of their associates, slowly 
draw the litter backward with alternating fore- 
feet, and then settle to sternal recumbency with 
the snout hidden beneath the litter, seemingly in 
an etfort to keep warm. Intermittent attacks of 
chilling shake the body, the reflexes are dulled, 
the eyes closed, and a general stupor prevails. 

Conjunctivitis, mild or severe, is practically al- 
ways present, causing an exudate of a seromucous 
or seropurulent type to appear, gumming the eye- 
lids together, or forming crusts which remain in 
the internal canthus and on the margins of the 
lids. 

Early in the attack, constipation is noted. The 
fecal balls, usually dark in color and often cov- 
ered with mucus, are voided with difficulty. 
Later, if death does not ensue, diarrhea sets in, 
and continues pending the advent of death or con- 
valescence. The character of the food determines 
the color of the feces. 

As the sick hog lies undisturbed in the nest 




'o 

bJO 
o 



03 



o 






37 



38 HOG CHOLERA 

there is often noted a scarcely audible, high- 
pitched, complaining expiratory grunt, but if the 
animal is seized suddenly it struggles feebly and 
emits a weak, hoarse squeal. The gait may be 
unchanged, but often staggering is noticed, and 
sometimes there is a characteristic unsteadiness 
or wea\ing in the hind quarters, best observed in 
well advanced cases when the animals are caused 
to move without undue excitement. 

Convulsions appear somewhat infrequently, and 
may be regarded as the only violent hog cholera 
symptom. The attack usually occurs at feeding 
time or under stress of other excitement, more 
often in young pigs. The pig comes to the trough 
as if to eat, but suddenly backs away, squealing, 
with the snout drawn low between the forelegs. 
The muscles stiffen in spasm, the pig falls on its 
side, the eyeballs roll upward, the legs are in con- 
stant motion, and the snout is gradually extended 
with a jerky, convulsive movement. The attack 
lasts less than a minute and terminates either in 
death or complete return of nervous function. 

Early in an attack of hog cholera, the skin is 
flushed, hot and sensitive, the flush being appar- 
ent only in clean white pigs. Later, as death ap- 
proaches, a diffuse purplish discoloration some- 
times appears in the skin covering the ears, snout, 
belly and inner surfaces of the legs, and is less 
frequently observed at the extremity of the tail. 



SYMPTOMS AND LESIONS 39 

on the vulva, and in the perineal region. Depend- 
ing on whether the color results from hyperemia 
or hemorrhage, it will or will not disappear on 
pressure. Sometimes congestion and hemorrhage 
coexist, in which case the color disappears for the 
most part, revealing the presence of ecchymoses 
in the pressure-whitened area. Less frequently 
ecchymoses exist alone. Somewhat infrequently 
skin ulcers appear on the throat and between the 
forelegs, very rarely elsewhere on the body. 
They are light brown, irregularly round or oval 
in shape, 1/2-2 centimeters in diameter, and cov- 
ered with scabs. A rusty yellow, very sticky exu- 
date, most apparent on the ventral scantily-haired 
body surfaces, is noted in some individuals. 

Cough is observed in many field outbreaks, but 
it is by no means a constant symptom in uncom- 
plicated hog cholera. We have failed to establish 
a definite relation between this symptom and the 
petechial hemorrhages which appear in the laryn- 
geal mucosa. Respiratory symptoms are not 
prominent in hog cholera unless it is complicated 
with pneumonia, but dyspnea develops frequently 
under forced exertion. 

The superficial inguinal lymph glands are fre- 
quently enlarged so as to attract attention, and 
another common symptom is the collection of urine 
in the sheath of the male pig, causing marked dis- 
tention. When pressed out manually, the urine 



40 HOG CHOLEEA 

has a very offensive odor, and may be cloudy white 
in appearance, or otherwise abnormal. 

As the disease progresses, emaciation is quite 
rapid, and general weakness prevails. Frequently 
a terminal pneumonia develops during the last 
few hours, and death may result from heart or 
respiratory failure. 

Chronic hog cholera occurs, for the most part, 
among stragglers that survive the acute form, but 
it may exist independently among semisusceptible 
young pigs. Emaciation, cough, depraved appe- 
tite, diarrhea, unsteady gait, drooping ears and 
tail, tucked-up flank, and even sloughing of the 
skin are among the symptoms that appear. Some 
animals recover, but complete return to normal 
health is not the rule. 

LESIONS 

Peracute hog cholera does not usually produce 
characteristic macroscopic lesions, but congestion 
of the lymph glands, mesenteric vessels and var- 
ious parenchymatous organs may often be ob- 
served. It is in the acute uncomplicated form 
that the most t^^pical lesions occur. These con- 
sist of congestion, hemorrhages and degeneration, 
hemorrhages being the only ones which, by virtue 
of character or location, are highly characteristic 
of the disease. These appear as petechias in the 
kidneys, serosa of the intestines, mucosae of the 



SYMPTOMS AND LESIONS 41 

bladder and larynx, in the pericardium, epicar- 
dium, and on the auricles of the heart, especially 
the left. Exceptionally they are seen in the dia- 
phragm, in the parietal pleura and peritoneum, 
and subjacent connective tissue. In the lungs, the 
hemorrhages usually appear beneath the pleura 
as ecchymoses, more often in the ventral portions 
of the cephalic and cardiac lobes, but at other 
times unconfined to particular areas. In the 
spleen they appear as well-defined slightly raised 
black areas 14 to ll^ centimeters in diameter, 
practically always at the edge of the organ and 
visible beneath its capsule from the dorsal aspect. 
Some of the lymph glands are practically always 
congested or hemorrhagic. The hemorrhage ap- 
pears first around the periphery as the sectioned 
surface will show, later extending to the trabec- 
ulse, and finally in some cases progressing so far 
that the entire structure becomes infiltrated, show- 
ing on section a uniform dark color. Petechiae 
and ecchymoses in the lymph glands are excep- 
tional. The nodes most regularly involved in- 
clude the gastric, hepatic, lumbar, superficial in- 
guinal, mediastinal and submaxillary. 

The hemorrhages which are found in and be- 
neath the alimentary mucosa may appear in the 
form of petechiae or ecchymoses, but there is a 
marked tendency, due probably to constant me- 
chanical irritation, for them to become more 



42 HOG CHOLEKA 

diffuse in character. The pharynx and esophagus 
are rarely affected, the stomach and small intes- 
tines frequently are, while the mucosa of the 
cecum and upper colon usually is involved. 

The skin lesions may consist of congestion or 
hemorrhage of circumscribed or diffuse nature, 
the latter type being by far the most common, and 
appearing as a purplish discoloration usually con- 
fined to the ears, belly, snout, inner surfaces of 
the legs, tip of tail, vulva, and perineal region. 
Small skin ulcers less than two centimeters in 
diameter, irregularly round or oval in shape, 
brown in color and scabbed over, appear somewhat 
infrequently on the throat, very exceptionally 
elsewhere on the body. These seemingly take 
origin from previous hemorrhages. 

Some have considered all these changes as due 
to secondary invasion, holding to the belief that 
hog cholera virus in itself does not produce mac- 
roscopic lesions. To this view we are unable to 
subscribe, for one may transport filtered virus 
hundreds of miles, and it will still produce, regu- 
larly, some or all of the leions just described, and 
it is inconceivable that the same secondary in- 
fluences should be present in all localities. 

In order to place in relief the more character- 
istic macroscopic lesions which, according to our 
conception, are due usually to unaided action of 
the filterable hog cholera virus, we have for the 



SYMPTOMS AND LESIONS 43 

moment neglected discussion of less characteris- 
tic changes which frequently take place. If we 
consider each organ separately, extending our ob- 
servations to include less characteristic changes, 
as well as those produced by secondary invaders 
discussed in a previous chapter, a more complete 
picture, and a more accurate interpretation^ of the 
pathological anatomy encountered in field cases 
can be presented. 

Mouth and pharynx. Mucosa usually normal. 
Hog cholera virus may be primary cause of ulcers. 
These are sometimes present in hog cholera out- 
breaks, and appear as dark brown necrotic patches 
on gums, lips, tongue and other parts. Probably 
due to primary injuries caused by the filterable 
virus, and certainly caused by B. necrophorus as 
a secondary invader. B. necrophorus ulcers oc- 
cur independent of filterable virus infection. 

Stomach. Mucosa frequently normal. Filter- 
able virus causes petechiae, ecchymoses or larger 
suffusions in fundus. Congestion due to the same 
cause usually present. Ulceration relatively rare, 

^ We are fully aware that with our present knowledge such an 
interpretation can be only approximately correct, but nevertheless 
there are certain well-defined tendencies which should be indicated. 
Our conception of the primary filterable virus lesion has been 
gained, during the last ten years, by performing autopsies on 
hundreds of pigs which were killed about a week subsequent to 
injection with virus. The virus was obtained from several sources 
in various states, some was filtered, some was not. We have also 
investigated several of the secondary invaders, and the combined 
results of these investigations with those of similar nature con- 
ducted by other workers, are reflected in the remarks which follow. 



44 HOG CHOLERA 

but necrotic patches due to secondary infection 
with Bact. necrophorus may appear. Serosa usu- 
ally normal. Exceptionally studded with puncti- 
form hemorrhages, due to filterable virus. 

Small intestine. Mucosa sometimes normal. 
Congestion rather common, also hemorrhages sim- 
ilar to those observed in stomach, and due to filter- 
able virus. Lymphoid nodules often congested, 
less frequently hemorrhagic, due to filterable vir- 
us. Those in ilium most frequently involved. 
Ulceration rather uncommon, except in extreme 
posterior portion of ileum. Serosa usually nor- 
mal. Petechial hemorrhages appear infrequently, 
mesentery often congested. Changes due to filter- 
able virus. 

Caecum and upper colon. Mucosa most con- 
stant seat of digestive canal lesions, especially 
region of iliocecal valve. Congestion, petechiae, 
ecchymoses' and larger suffusions common. 
Strong tendency toward ulceration. Pitlike 
patches denuded of epithelium. Necrptic ulcers 
or patches, dark brown in color, sometimes false 
membrane ; ulcers tending to broaden and deepen, 
little tendency toward regeneration. '' Button 
ulcers ' ' ^ occur in chronic hog cholera. Serosa 

* The ulcers may be isolated and appear as circular, slightly 
projecting masses stained yellowish or blackish or both in alter- 
nate rings, or they may be slightly depressed and somewhat ragged 
in outline. When the superficial slough is scraped away many 
ulcers show a grayish or w'hite base. A vertical section reveals a 
rather firm neoplastic growth, extending usually to the inner mus- 



SYMPTOMS AND LESIONS 45 

often normal, petechiae not infrequent. Hemor- 
rhages and destruction of epithelial cells probably 
due to filterable virus. ^'Button ulcers'' due to 
B. siiipestifer, possibly to other organisms. 
Necrotic patches usually due to Bad. necro- 
pliorim. 

Lower colon and rectum. Usually normal or 
nearly so. Sometimes congested. Infrequently 
the lower colon shows the same change as the 
upper colon. 

Lar5aix. Mucosa frequently normal. Some- 
times congested, more often dotted with petechias 
caused by filterable virus. 

Trachea and bronchi. Mucosa often normal. 
Sometimes congested. Probably due to filterable 
virus. 

Lungs. Very often normal. Primary lesions 
sometimes caused by filterable virus consist of 
ecch}Tnoses visible beneath the pleura. These ap- 
pear most frequently on the cephalic and cardiac 
lobes, but are not confined to these parts. 

Terminal pneumonia due to filterable virus plus 
nonspecific secondary invaders. Often affects all 

cular coat. When sections of such an ulcer are stained with 
aniline dyes and examined under the microscope, the submucous 
tissue is very much thickened, infiltrated with round cells and con- 
taining a large number of dilated blood vessels. Resting upon 
this thickened submucosa, is a line of very deeply stained amor- 
phous matter, and upon this is situated the necrotic mass which 
fails to retain the coloring matter and which is permeated by a 
very large number of bacteria of various kinds. Frequently the 
eggs of trichocephalus are imbedded in the slough. ' ' — Moore, 
Pathology of Infectious Diseases. 



46 



HOG CHOLERA 



lung tissue. Lung solidified, red. Pneumonia of 
recent origin. 

Swine plague pneumonia due to filterable virus 




Plate 2. Lung of pig showing ecchymoses due to acute hog 

cholera. These appear in greater numbers on the 

apical and cardiac lobes 

plus Bad. suisepticum. Cephalic and cardiac 
lobes first to be affected, later other parts may 
solidify. Solidified portion usually red or reddish 
gray. Usually bronchopneumonia. Interlobular 



SYMPTOMS AND LESIONS 47 

spaces well defined macroscopically, due to infil- 
tration of leucocytes or blood. Tendency toward 
necrotic and caseous masses in cases of longer 
standing. Pleuritis constant. Pleurae often 
thickened, rough, white, adherent. 

Pneumonia, characterized by necroses which 
start from various foci, tending to involve all 
structures alike, sometimes spreading to the heart 
by contiguity. Filterable virus plus Bad, necro- 
phorus. 

Pneumonia, often semichronic, tending toward 
formation of multiple abscesses visible beneath 
the pleura, as slightly raised, yellow areas. Visi- 
ble on section in deeper parts. Pneumonic lung 
may be red. More often grayish in color. Due 
to filterable virus plus B. pyocyaneus} 

Heart. Usually normal. Filterable virus le- 
sions consist of petechias and ecchymoses which 
are visible on the surfaces of the auricles, usually 
the left. Sometimes congestion of coronary ves- 
sels. Heart itself rarely the seat of secondary le- 
sions. Epicarditis and pericarditis often result 
from secondary infection with Bad. suisepticum. 

Spleen. Sometimes normal or slightly en- 
larged. Very small bright-red protruding hem- 

^ Hog cholera virus is only one of several influences capable of 
producing primary changes which, in the presence of secondary 
invasion with either Bad. necro phorus or B. pyocyaneus may re- 
sult in the lung lesions mentioned in connection with these organ- 
isms. For instance, we regard lung worms in combination with 
B. pyocyaneus as a frequent cause of pneumonia in pigs. 




'o 

o 



■73 



be 



_bJC 
'S. 



o 






48 




Plate 4. Spleens showing^ hemorrha,2:es which are 
rather typical of acute hog cholera. These 
hemorrhages are observed in. only a small per- 
centage of cases 

49 



50 HOG CHOLERA 

orrhages beneath capsule are normal. These are 
frequently on ventral surface near the hilus, not 
so often along the borders and on the dorsal sur- 
face. Characteristic filterable virus lesions con- 
sist of black, well defined slightly raised hemor- 
rhages 1/4 to 2 centimeters in diameter, located 
practically always somewhere on the margin. 
Spleen may be enlarged, dark, friable, engorged 
with blood. Due usually to secondary invasion 
with B. siiipestifer, sometimes to other causes. 
Not of much diagnostic value as related to hog 
cholera. 

Liver. Macroscopic appearance usually nor- 
mal. Very exceptionally ecchymoses, seemingly 
due to hog cholera virus, are visible beneath the 
capsule. Often shows degenerative changes, 
probably due to hog cholera virus, but by no means 
characteristic, as they may be due to a variety of 
causes. 

Kidney. Very rarely normal. Seat of the 
most characteristic and constant hog cholera le- 
sions, consisting of petechias. Organ may be 
changed as follows: 

Normal in color, capsule peels easily. Surface 
of kidney studded with petechiae w^hich appear 
beneath the capsule, involving the glomeruli as 
well as other parts. On section, the petechiae are 
seen variously distributed in the cortex, in the 
medulla, and sometimes in the membrane of the 




Plate 5. Kidney of pig showing numerous 
petechia due to acute hog cholera. Often 
these petechias are so small and few in num- 
ber that it is necessary to examine the kid- 
ney very closely in a good light in order to 
observe them. The capsule is removed in 
order to make them more plainly visible 

51 



52 HOG CHOLEEA 

renal pelvis. They are due to the filterable 
virus. 

Engorged with blood. Capsule peels easily. 
Petechiae distributed as already described. Tend- 
ency toward more and larger hemorrhages. 
Changes usually due to filterable virus. Bact. 
suisepticum or B, cholera suis may be secondary 
invaders. 

Very light in color, '^cooked kidney.'' Capsule 
peels easily. Marked evidences of degeneration. 
(Cloudy swelling and granular degeneration.) 
Petechiae distributed as already described. All 
changes probably due to filterable virus. 

Very light in color. Capsule peels easily. No 
petechiae. Seen most frequently in chronic hog 
cholera. Changes often due to filterable virus, 
but not characteristic of it. 

Very light in color. Capsule peels mth diffi- 
culty, may be thickened. Evidences of degenera- 
tion followed by increase in interstitial tissue, and 
chronic nephritis. Primary degeneration prob- 
ably due to filterable virus. Nephritis due to sec- 
ondary causes. All of these dianges of little 
diagnostic significance. 

Considered in general, these petechial hemor- 
rhages in the kidney are rarely due to influences 
other than hog cholera virus. Exceptionally they 
may be due to Bact. suisepticum, acting either as 



SYMPTOMS AND LESIONS 53 

a primary or secondary influence. There is a 
tendency by no means constant, and of little diag- 
nostic significance, for larger and less well defined 
hemorrhages to appear under the influence of 
Bact. siiisepticum. There is also some evidence, 
as yet poorly substantiated, that very exception- 
ally Bact. necrophorus produces petechias in the 
kidneys of hogs. This should be regarded as a 
remote possibility occurring only in association 
with extensive necrotic lesions in other organs. 

Bladder. Sometimes normal. Mucosa slightly 
congested, due to hog cholera virus or other 
causes. Mucosa dotted with petechiae, due usu- 
ally to hog cholera virus. 

Sheath. Often normal. Sometimes distended 
with foul smelling, discolored urine. Catarrhal 
inflammation of mucosa. Condition not charac- 
teristic of hog cholera. Found in other diseases, 
especially those resembling rheumatism. 

Lymph glands. Sometimes normal. Typical 
filterable virus lesion consists of congestion or 
hemorrhage which appears first in the cortex of 
the gland, and which may later involve the entire 
structure giving it a uniform dark color on section. 
Petechiae are rarely present. Edema frequently 
pronounced. Permanent enlargement and casea- 
tion occur in chronic hog cholera. Rare for all 
glands to show macroscopic changes. Glands 



54 



HOG CHOLERA 



most frequently affected are the gastrics, hepatics, 
superficial inguinals, lumbars, submaxillaries and 
mediastinals. 




Plate 6, Lymph glands of pig showing hemorrhages caused by acute hog 
cholera. Left, darkened surfaces of glands. Above, sectioned surface 
showing hemorrhages around the periphery and in the sinuses. Eight, 
darkened gland with small section cut away to show peripheral 
hemorrhages 

Skin. Often normal. Typical filterable virus 
lesions consist of purplish discoloration, repre- 
senting marked congestion or diffuse hemor- 



SYMPTOMS AND LESIONS 55 

rhage. Ecchymoses more rarely visible. Ulcers, 
apparently originating in these ecchymoses some- 
times occur on throat and between forelegs. (In 
hot weather purple discoloration appears a few 
hours after death in hogs, especially fat ones, 
dead from any cause.) 

The pathology and microscopic tissue changes 
produced by hog cholera virus are not well worked 
out, but nevertheless the relation between primary 
filterable virus lesions and secondary changes due 
to other causes is fairly well understood. Let us 
consider, for instance, lesions of the digestive mu- 
cosa. Congestion appears first. It will disap- 
pear or terminate in hemorrhage. Follomng 
hemorrhage, regenerative or degenerative pro- 
cesses will occur. The degenerative processes 
may result in destruction and excoriation of the 
epithelial cells, leaving an unprotected surface in 
contact with the intestinal contents. Individual 
resistance and the bacterial flora of the intestine 
will determine future developments. Regenera- 
tion will rule, or secondary infection will take 
place. If Bad, necropJiorus is present in suffi- 
cient numbers, necrotic enteritis will be produced. 
If B. suipestifer exists in overpowering numbers, 
the familiar ^^ button ulcer'' may develop. 

In the intestine, we find the primary lesions due 
to the filterable virus most frequently in the cae- 



56 HOG CHOLERA 

cum and upper colon, and as would be expected, 
we find the secondary lesions distributed in pre- 
cisely the same manner. If we examine a hog 
dead of cholera after a short sickness we encoun- 
ter intestinal lesions in which congestion, hemor- 
rhages and early evidences of degeneration pre- 
dominate. In hogs that have been sick longer, 
autopsies often reveal a surprising variety of le- 
sions which collectively encompass effects of the 
struggle between degenerative and regenerative 
forces, and which reach their most typical form in 
the ^ ' button ulcer. ' ' 

In considering thoracic lesions, the same general 
principles apply. If we inject a pig with filtered 
hog cholera virus, and kill it about seven days 
later, the lungs, if affected, will show petechiae 
and ecchymoses, most likely appearing on the 
cephalic and cardiac lobes, but not always confined 
to these parts. There may also be congestion of 
the mucosa of the air passages. Both changes 
are due to the filterable virus. What result 
would we expect if a secondary invader, capable 
of producing inflammatory changes, should find 
its way into lesions thus prepared? Obviously we 
would expect to find bronchopneumonia, occurring 
most regularly in the cephalic and cardiac lobes 
but not always thus limited. It is significant that 
this is the exact picture presented when secondary 
infection with Bad. suisepticum takes place. 



SYMPTOMS AND LESIONS 57 

The urine of hogs suffering with cholera often 
contains albumin in excessive amounts, and the 
chlorids frequently are diminished in quantity, or 
present only in traces. Contrary to what might 
be expected, blood and hemoglobin are absent, al- 
most without exception. 



CHAPTER VI 

DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 

Early and correct diagnosis of hog cholera is 
essential in coping with the disease effectively. 
Often an entire herd is in jeopardy, and if hog 
cholera is present prompt preventive measures 
must be taken to save it. The diagnosis involves 
no great difficulties when many hogs are sick, but 
in the early days of an outbreak when peracute 
or otherwise atypical cases are likely to occur, 
puzzling situations arise which sometimes cause 
costly delay. Thus in exceptional cases we are 
justified in making a provisional diagnosis of hog 
cholera, and in handling the herd in exactly the 
same manner as we would were a positive diagno- 
sis possible. Experience has taught that we 
should not be too conservative in regard to taking 
such a course when the history suggests the dis- 
ease and when valuable animals are at stake. 

In seeking to determine the presence of hog 
cholera we depend on four considerations: 

1. History of the outbreak. 

2. Symptoms. 

3. Lesions. 

58 



DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 59 

4. Animal Inoculation (rarely applicable). 

History. Securing the history of an outbreak 
of suspected hog cholera is simply applying knowl- 
edge of the ways in which the virus spreads. 
Usually we find that a hog has died of an unknoAvn 
cause and a few days later sickness has appeared 
among its associates. Careful inquiry should be 
made regarding recent introduction of hogs into 
the herd, existence of swine disease in the vicinity, 
adjacent arteries of traffic and source of feed and 
water supply. Stockyard hogs and others intro- 
duced without clear history of previous health 
should remain under suspicion. Even though 
they do not themselves contract the disease they 
may act as intermediate carriers. There is no 
evidence that hog cholera virus travels through 
the air but a road or railroad right-of-way may be 
contaminated by the drip from infected wagons or 
cars. If the herd is subsisting on garbage and is 
not immune the circumstances suggest hog chol- 
era. If kitchen swill is being fed inquiry should 
be made as to whether the kitchen is supplied with 
market pork.^ 

In general the facts brought out by the history 
of an outbreak simply constitute supplementary 

^ In one instance that came under our observation an outbreak 
of hog cholera was traced to meat trimmings that were placed in 
a poultry house. Two small pigs formed the habit of escajDing 
from the pen and eating freely of these trimmings. Both devel- 
oped hog cholera simultaneously, and later transmitted it to their 
associates. 



60 HOG CHOLERA 

evidence tending either to affirm or deny the pres- 
ence of hog cholera. Unless there is a definite 
history of direct exposure the history in itself is 
not conclusive. 

Symptoms. Unless several animals are sick it 
is seldom possible to make a positive diagnosis 
based on symptoms alone, but the experienced ob- 
server is usually fairly certain of his ground. 
It is essential to remember that early in an out- 
break we do not observe the greatly emaciated 
hog with arched back, straight tail and drooping 
ears which has been so frequently described and 
photographed, and which is the product of long- 
sickness. It should also be kept in mind that 
many of the symptoms observed in acute hog 
cholera are present in other diseases, and that all 
of the symptoms that characterize the disease, do 
not often appear in one animal. Special consid- 
eration must be given to a restricted number of 
the more characteristic symptoms. 

In examining a herd for suspected hog cholera 
one should first see it unaffected by artificial ex- 
citement, taking care to observe a tendency in 
individuals to chill and crawl beneath the litter. 
Then the animals may be tempted from the nest 
with feed, observation being made for any that are 
reluctant to move, or that stagger or weave in the 
hind quarters. The animals that come greedily to 
the trough but leave for the nest in advance of 



DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 61 

their associates, dropping slowly to sternal recum- 
bency with their snouts half buried in the litter 
should be regarded as probable cases of hog chol- 
era, especially when intermittent attacks of chill- 
ing are observed. 

Temperature is an important guide, but great 
care must be taken in securing and interpreting 
readings. Normal temperatures of hogs vary be- 
tween 101° and 104° F. and independent of dis- 
ease, excitement or exertion causes a more rapid 
temperature elevation in swine than in other ani- 
mals. Docile adult breeding animals in medium 
flesh are inclined to show readings near 101° F., 
while those of young pigs and fat hogs tend to ap- 
proach 104° F. In taking temperatures of pigs, 
the thermometer, preferably one with pear or 
globe-shaped bulb and at least five inches long, 
should be inserted almost full length. Otherwise 
many inaccuracies (readings too low) will occur, 
because a pig, especially if held by the hind legs, 
will often relax the rectum as long as the ther- 
mometer remains in position. Chasing pigs to 
catch them often elevates their temperatures 
rapidly, and should be avoided. 

It is important to keep in mind the usual hog 
cholera temperature curve. In the typical case 
of the acute form of the disease the curve rises 
rapidly at the onset of the attack and reaches 
an elevation between 106° and 107° F. in less than 



62 HOG CHOLERA 

forty-eiglit hours. This level is maintained for 
about four days and is followed by a sharp decline 
which may bring it near normal for a few hours. 
Then there is an upward trend which carries it 
near the former high level in which position it 
may be maintained, or it may fluctuate somewhat 
violently from day to day. Sometimes it remains 
elevated until death takes place, but usually it 
sinks below normal a short time before the pig 
dies. 

Thus it is always well to secure temperatures 
of hogs recently affected, and to be cautious in 
regard to making a negative diagnosis on the 
strength of a limited number of temperatures near 
normal. Several readings near or above 106° F., 
supported by other suspicious symptoms and a 
history that indicates hog cholera, may rightly 
form the basis for a provisional diagnosis. On 
the other hand, a considerable number of tempera- 
tures below 104° F. in sick hogs, strongly suggests 
some other disease. Between these extremes the 
readings are less conclusive. 

In this country, and in others where swine ery- 
sipelas is not prevalent, the characteristic diffuse 
purplish discoloration which appears on the belly, 
ears and snout is pathognomonic of hog cholera, 
but it is observed in relatively few cases. If this 
discoloration is not observed before death it is 
of no significance, for it may occur as a post-mor- 



DIAGNOSIS, DIFFEKENTIAL DIAGNOSIS, PROGNOSIS 63 

tern change in swine dead from any cause, es- 
pecially fat hogs that have died in hot weather. 

Other less characteristic symptoms add evi- 
dence, but most of them may result from causes 
other than hog cholera, and it is unsafe to give 
them too much weight in their relation to diagno- 
sis. 

Lesions. Lesions constitute our most accurate 
guide in diagnosing hog cholera, for it is not often 
that a conclusion can be reached without consider- 
ing them. Hogs sometimes die of the disease 
without showing any characteristic macroscopic 
tissue changes, so if no cause for death is found, 
additional autopsies should be performed. In 
case it is necessary to kill a pig for this purpose, 
it is best to select one that has been sick several 
days, but not a chronic case. Petechiae and ec- 
chymoses are the chief changes which character- 
ize hog cholera, but it is important to remember 
that in cases of long standing, and in those in 
which secondary invasion has taken place these 
primary filterable virus lesions may be so changed 
in character that they are difficult to identify. 

Assuming that we have before us a carcass, and 
that hog cholera is suspected, the autopsy will in- 
clude special examination of the skin, kidneys, 
bladder, lymph glands, spleen, heart, lungs and 
laryngeal mucosa, as well as the serous membranes 
readily accessible, and the digestive tract. The 



64 HOG CHOLEKA 

changes which appear in these various parts have 
already been discussed, so for our present purpose 
we will consider chiefly those which are of primary 
importance in their relation to diagnosis. 

The skin is examined for ecchymoses and yel- 
lowish-brown ulcers which sometimes appear on 
the throat and other ventral surfaces. If there 
is a purplish discoloration, inquiry should be made 
as to whether it was noticed before death took 
place. An affirmative reply suggests hog cholera, 
while a negative one practically dismisses the le- 
sion from consideration. Changes in the skin are 
frequently absent. 

As we open the thoracic and abdominal cavi- 
ties petechiae and ecchymoses are sometimes ob- 
served in or immediately beneath the serous sur- 
faces thus exposed. They appear infrequently in 
the parietal pleura and parietal peritoneum and 
are somewhat more common in the serous coat of 
the intestine, especially that of the cecum and 
colon. 

The kidney lesions are highly characteristic of 
hog cholera, and they occur in nearly all cases. 
They consist of petechiae which are distributed on 
the surface, as well as in the deeper structures. 
These are dark red in color and sharply defined, 
often giving the organ the 'Hurkey egg^' appear- 
ance. Sometimes they are so few in number that 
the capsule must be removed in order to see them, 



DIAGNOSIS, DIFFEEENTIAL DIAGNOSIS, PROGNOSIS 65 

care being taken to make the examination in a 
strong light. Infrequently other causes produce 
petechige in the kidneys of swine, but in this coun- 
try, unless another cause is apparent, either by 
virtue of the history or accessory lesions, we are 
safe in attributing them to hog cholera. 

Petechi^e in the mucosa of the bladder occur in 
most cases of hog cholera, and they do not often 
result from other causes. The serous surface is 
practically always normal. 

Some of the lymph glands are usually involved, 
and to the experienced observer the changes in 
them aid greatly in making a diagnosis. On the 
surface the gland is very dark red, almost black. 
On section the periphery is similar in color, while 
the deeper structures may remain unchanged. It 
is important to bear in mind that any inflamma- 
tory process may aif ect adjacent lymph nodes, and 
to make allowance for this fact, but marked per- 
ipheral congestion or hemorrhage, when observed 
in several glands widely separated, in the absence 
of apparent inflammation in adjacent structures, 
strongly indicates hog cholera. 

The spleen reveals characteristic hog cholera le- 
sions only in the dark, swollen circumscribed hem- 
orrhages, usually less than 1 centimeter in diam- 
eter, which appear along the border. In field 
cases that have died of hog cholera these lesions 
are not often observed, because secondary invad- 



66 HOG CHOLERA 

ers have so enlarged and darkened the entire or- 
gan as to render them invisible, and because post- 
mortem changes take place rapidly. The enlarged, 
dark, pulpy spleen which is often encountered in 
hog cholera outbreaks is of little significance in 
diagnosis, because it is so frequently the result of 
other causes. 

The heart reveals no macroscopic lesions in the 
vast majority of cases, but the petechise which are 
sometimes visible on the left auricle, less fre- 
quently on the right, and rarely involve the ven- 
tricles, are usually caused by hog cholera virus. 

The lungs are often normal. If the surfaces are 
dotted with ecchymoses, the fact suggests hog 
cholera quite strongly, but occasionally these le- 
sions are due to other causes. 

The laryngeal mucosa is often the seat of pete- 
chiae, which are characteristic of hog cholera. 

Examination of the intestinal mucosa often aids 
in making a diagnosis, but the lesions encountered 
are often difficult to interpret. Certain irritants 
cause changes which may be confused with those 
due to hog cholera, and secondary invasion tends 
rapidly to modify filterable virus lesions so that 
they are difficult to identify. Ecchymoses and 
larger hemorrhages, as well as ulcers of recent 
origin, when distributed near the ileocecal valve 
and elsewhere in the mucosa of the caecum and 
upper colon, may be accepted as supplementary 



DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 67 

evidence of acute hog cholera. The ^^ button 
ulcer*' is usually associated with the chronic form, 
but agents other than the filterable virus may be 
instrumental in producing it. 

All these hog cholera lesions will not often be 
found in one animal, but if two or more organs 
are involved this fact, supported by a history 
that does not positively deny the presence of 
the disease, may be accepted as ground for a 
diagnosis. If more organs are involved the evi- 
dence is more conclusive. 

AnimaJ inoculation. This' method is rarely 
applicable in actual practice, because it is expen- 
sive and requires too much time. In very excep- 
tional outbreaks which present atypical features, 
and in cases involving litigation it may be useful. 
The essentials of a conclusive experiment may be 
summarized thus: 

1. Blood should be drawn from a hog which has 
been sick for only a short time, and which carries 
a temperature near 106° F. 

2. The blood should be diluted with sterile 
water and passed through a filter which retains 
all microscopic organisms. 

3. Enough of the filtrate to represent at least 
1 mil of the undiluted blood should be injected 
into a susceptible pig, preferably one weighing 
between forty and one hundred pounds. 

4. Twelve days previous and subsequent to the 



68 HOG CHOLERA 

date of injection the pig should be protected from 
extraneous hog cholera infection; all receptacles 
and instruments used in making the injections 
should be sterilized. 

5. Symptoms of hog cholera should appear in 
less than eight days following the injection. 

6. The pig should die in less than seven days 
following the appearance of symptoms, or at the 
end of that time, providing it is still sick, it should 
be killed. 

7. Autopsy should reveal typical hog cholera 
lesions in at least two organs. 

8. In negative experiments the susceptibility of 
the experimental pig should be proved by a subse- 
quent injection with at least 1 mil of virulent hog 
cholera blood. 

Differential Diagnosis 

Peculiar difficulties are met in the differential 
diagnosis. Clinical examination of the individ- 
ual is subject to limitations which are not encoun- 
tered in dealing with larger animals, and some of 
the maladies which we seek to differentiate from 
hog cholera occur so frequently in combination 
with that disease that we do not always have well 
defined features upon which to base our conclu- 
sions. Thus under certain circumstances we have 
not only to decide whether a given outbreak is 
hog cholera or swine plague, but we must also 



DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 69 

ask ourselves whether the two diseases exist in 
combination. Laboratory examinations may dem- 
onstrate the presence of a bipolar organism, but 
they cannot in the course of a few hours deny the 
presence of the hog cholera virus, and thus they 
are often dangerously misleading. Return mail 
diagnoses of '^ swine plague" or ' 4iemorrhagic 
septicemia" are without value because they ignore 
consideration of hog cholera virus, which in this 
country is present in most outbreaks of rapidly 
transmissible swine disease. 

Among the diseases from which hog cholera 
must be differentiated are uncomplicated swine 
plague, pneumonias due to a variety of causes, sep- 
ticemias, tuberculosis, anthrax, so-called ''flu," 
various parasitisms, soap poisoning, brine poison- 
ing, and sudden deaths from such causes as heat- 
stroke and lightning-stroke. Rouget and rinder- 
pest are also to be considered in countries in which 
they are prevalent. 

The differential diagnosis cannot be made by 
rule of thumb, nor is it possible to summarize 
or tabulate the determining features of these va- 
rious maladies, so that the inexperienced observer 
can distinguish among them. Armed mth defi- 
nite knowledge of the diseases with which he is 
dealing the diagnostician usually reaches his con- 
clusions rapidly and accurately. In the absence 
of such knowledge, a few rules do not suffice. 



70 HOG CHOLEKA 

Having already dealt with the distinguishing fea- 
tures of hog cholera we will confine our remarks 
chiefly to characteristics which suggest the pres- 
ence of these other diseases. 

Swine plague. Swine plague rarely occurs in 
pure form, it affects only a portion of the animals 
in a herd, and there are frequent spontaneous re- 
coveries. There is often a history of recent ship- 
ping. The incubation period is short (1 to 3 days), 
acute dyspnea and thumping are prominent symp- 
toms, and the hogs show more distress than is 
observed in hog cholera attacks. High tempera- 
tures are not the rule except during the first few 
hours of sickness. The characteristic ** swine 
plague pneumonia,^' if present in several autop- 
sies, speaks for the existence of swine plague, but 
the absence of the filterable hog cholera virus 
must be clearly established before a diagnosis of 
pure swine plague is justified. 

None of the pneumonias, with the exception of 
that associated with swine plague, are accom- 
panied by the lesions in other organs which char- 
acterize hog cholera. Usually they occur where 
pigs are kept in very dusty quarters, or where 
the floors are cold and damp and no dry litter is 
provided. Recent shipping is a predisposing fac- 
tor, and lung worm and ascarid infestations play 
an important part in their development. They 
are sporadic or only slowly transmissible. High 



DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 71 

temperatures are not common, and the prominent 
symptoms grow out of the pneumonia itself. 

Exceptionally septicemia due to nonspecific or- 
ganisms may occur, but its features are not well 
defined. In differentiating we must therefore de- 
pend on the more definite manifestations of hog 
cholera. 

Tuberculosis may only rarely be confused with 
chronic hog cholera. Hogs following tuberculous 
cattle and those fed infected creamery by-prod- 
ucts are most commonly affected. The history of 
the case should be considered and if doubt remains 
the intradermal tuberculin test may be applied. 
If material for autopsies is available, the differ- 
entiation presents no great difficulties. 

Anthrax and the peracute form of hog cholera 
are not always easy to differentiate. If the for- 
mer disease has existed previously in the locality ; 
if other classes of live stock are affected; if the 
hogs show swelling of the throat or froth mixed 
with blood coming from the mouth or nostrils ; if 
the blood is black and incoagulable, anthrax should 
be suspected, and a microscopical examination 
made. 

A malady known as ** state fair disease" or 
**flu** has in recent years been recognized in the 
central states. It is often associated with a his- 
tory of recent shipping, respiratory symptoms 
and lesions predominate, and recovery is the rule. 



72 HOG CHOLERA 

This latter fact alone will distinguisli it from hog* 
cholera, when it occurs in pure form. 

Ascaris infestation and hog cholera sometimes 
exist in the same herd. As a result of the diar- 
rhea incident to the latter disease ascarids are 
frequently evacuated in the feces, and the entire 
train of symptoms, as well as the deaths, is attrib- 
uted to the parasites alone. Even though the 
parasites are present in large numbers, if deaths 
are numerous, further examination should be 
made for evidence of hog cholera. 

Lung worms cause cough, emaciation and other 
symptoms which resemble those observed in 
chronic hog cholera. The history of the outbreak, 
supplemented if necessary by an autopsy, will be 
sufficient to determine its cause. Chronic hog 
cholera is usually a sequel of the acute form. 
Lung worms are often associated with pneumonia, 
causing death most frequently in young pigs. 
Unless great care is used these parasites may be 
overlooked. The smaller air passages should be 
laid open mth sharp shears and the examination 
made in a strong light. 

Considered collectively, the various drug and 
food poisonings differ from hog cholera in that 
several animals often are affected at the same 
time, the s^nnptoms as a rule are more violent, 
vomiting is more common, and temperatures are 
not so high. The history may reveal the source 



DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 73 

of the particular poison, and some of the drug 
poisonings (strychnin, belladonna, lead) are in 
themselves characteristic. Poisoning with the al- 
kaloids produces no lesions, and no poison, so far 
as we know, is responsible for changes which are 
observed in hog cholera. Common salt (sodium 
chlorid) is especially poisonous for hogs that are 
not accustomed to it, causing intense inflammatory 
changes in the digestive mucosa, and congestion 
of the meninges. Long continued feeding with 
material containing soap and lye will produce 
disease resembling chronic hog cholera. How- 
ever, our task is usually to differentiate between, 
poisonings and acute hog cholera, and this pre- 
sents no great difficulties if we resort to autopsies, 
for none of the poisons produce lesions w^hich re- 
semble those observed in acute hog cholera. 

In suspected heat-stroke and lightning-stroke, 
the history is. an important guide. Heat-stroke 
occurs most frequently in fat hogs deprived of 
shade or water in hot weather, and in those 
shipped in overcrowded stock cars, or subjected 
to excitement or violent exertion during the sum- 
mer months. The hair of hogs dead of lightning- 
stroke may be seared, there may be arborescent 
congestion or hemorrhage in and beneath the skin 
at the point where the current entered the body, 
and sometimes there are lacerations of the inter- 
nal organs. Rigor mortis is not pronounced. 



74 HOG CHOLERA 

Rouget or swine erysipelas does not exist in 
the United States. The septicemic form of the 
disease resembles hog cholera very closely. It 
has a shorter incubation period than the latter 
disease, but resort must often made to microscop- 
ical examination, in order to distinguish between 
them. 

Rinderpest does not occur in the United States, 
and in countries in which it is prevalent, swine do 
not contract it readily. For this reason it is not 
well characterized, but in case of necessity it may 
be distinguished from hog cholera by filtration 
experiments in which cattle are used as test ani- 
mals. Both viruses are filterable, but that of 
rinderpest is the only of the two which affects 

bovines. 

Prognosis 

In the individual, hog cholera runs a rapid and 
fatal course, and even when recoveries occur, they 
may be slow and incomplete. Therefore in all 
hogs visibly sick the prognosis is bad, but it is the 
herd as a unit which we must consider, for we are 
frequently called on to estimate the salvage which 
may be expected. The ability to do this Avith a 
reasonable degree of accuracy is acquired only by 
experience, and it is a great asset to one who han- 
dles hog cholera in the field. We can indicate only 
the guiding principles upon which the progno- 
sis depends. 



DIAGNOSIS, DIFFEEENTIAL DIAGNOSIS, PROGNOSIS 75 

The number of animals dead and visibly sick 
at the time of serum treatment forms our chief 
basis of estimate. Assuming that a herd is kept 
under average farm conditions, and that there is 
no evidence of complications, as a very general 
rule we expect to save about as many hogs as are 
eating greedily and are free from abnormal tem- 
peratures on the date of serum administration. 
Some of those that show no fever will die, and a 
few of those that show fever will recover, one 
class approximately compensating the other. 

In herds in which it is not possible to secure 
reliable temperature readings, the prognosis must 
be more guarded. In general, during the early 
days of an outbreak, we expect about as many 
deaths to follow serum treatment as the combined 
sum of the hogs that have previously died and 
those visibly sick when serum is administered. 
If fifty per cent of the animals in a herd are dead 
or visibly sick we expect the salvage to offset the 
cost of serum treatment, and leave something to 
spare, but we cannot promise much in such a herd. 

Evidence of secondary infection, coexisting par- 
asitisms, improper feeding and housing, a history 
of recent shipping or other weakening influences 
all call for a guarded prognosis. If the hogs have 
not been confined closely, or if they are in several 
pens some of which remain uninfected, the prog- 
nosis is relatively more favorable. 



CHAPTER VII 

PEEPARATION OF ANTI-HOG-CHOLERA SEEUM AND HOG 

CHOLERA VIRUS 

We are indebted to Dr. Marion Dorset and Dr. 
W. B. Mies of the United States Bureau of Ani- 
mal Industry for developing our present method 
of preparing anti-hog-cholera serum. The dis- 
covery that hog cholera is caused by a filterable 
virus dismissed further efforts to immunize 
against it with products of various bacteria, but 
it suggested hope for a protective serum analo- 
gous to that used against rinderpest, a filterable 
virus disease of cattle. That hope was realized 
in 1908 when Dorset announced his discovery, and 
although the immediate control of hog cholera 
which some predicted did not materialize, the ob- 
stacles encountered have not been due to any fun- 
damental defect in the serum itself. When prop- 
erly prepared and used it is one of the most effec- 
tive biologies knoAvn to preventive medicine. 

Anti-hog-cholera serum production is highly or- 
ganized and carefully controlled in the United 
States and many laboratories are in operation 

which are models for convenience, cleanliness and 

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78 HOG CHOLEKA 

sanitation. All laboratories which make inter- 
state shipments must secure licenses from the fed- 
eral government and submit to regulations which 
have been formulated to protect those who use 
the products. The laboratories must meet certain 
well-defined requirements before they are allowed 
to operate, and thus despite great deviation in de- 
tail, the same fundamental processes are used in 
all of them. AVe will consider tirst the essential 
requirements for preparing the protective defib- 
rinated blood, which has been called anti-hog-chol- 
era serum, and which forms the basis of all the 
more or less refined products used to prevent hog 
cholera in the field. 

Buildings. The buildings should be suited to 
the conditions under which the laboratory is to 
operate. These conditions vary so Avidely that 
uniformity is neither to be expected nor desired, 
but certain governing principles should be ob- 
served in all construction. In general, simplicity, 
convenience in operation, and provisions for clean- 
liness are the primary considerations. Future up- 
keep costs should also be reduced to a minimum 
in the original construction. Under most condi- 
tions concrete is the best material to use. 

The walls, ceiling and floors should be fin- 
ished so that water will not injure them. The 
floors should be drained in a sanitary manner. 
Steam or hot water heat should be provided, the 




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80 HOG CHOLERA 

building should be plumbed for hot and cold 
water, and all outside doors should be screened in 
summer. Ample light and ventilation are re- 
quired. 

The minimum requirements for reasonable con- 
venience and cleanliness in a serum laboratory 
consist of preparation room, bleeding room, serum 
laboratory proper, office, dressing room and lava- 
tories, store room and refrigerator room, as well 
as furnace room and coal bins so situated that 
dust from them will not contaminate other parts 
of the building. 

Quarters for the hogs should be suited to local 
requirements. In any event they should be at 
least seventy-five feet from the laboratory build- 
ing, and even a greater distance is desirable. 
The floors should be of concrete, w^ell drained, 
and ample light and ventilation should be pro- 
vided. Room for exercise on the ground is desir- 
able, and pasture for hogs that are to be kept 
for several weeks is a great asset. Provision 
should be made for sanitary disposal of manure, 
and other waste from the laboratory and hog 
quarters. In general, convenience for those who 
care for the animals, and cleanliness and comfort 
for the animals themselves are the chief consid- 
erations. 

The equipment of the laboratory is likewise 
governed by individual needs. Too much equip- 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 81 

ment is a detriment, as methods are constantly 
changing and improving and each mmecessary fix- 
ture takes up room and must be kept clean. Es- 
sential major equipment includes facilities for 
washing, sterilizing and storing all instruments 
and containers used, vacuum and pressure tanks 
connected with motor driven pumps, portable 
crates for tail bleeding and hypering, portable or 
stationary tables or stocks for bleeding serum hogs 
and virus pigs from the throat, scales,^ motor 
driven shaker, serum mixer and office equipment 
including forms for keeping records. 

Minor equipment includes bleeding and hyper- 
ing units, tail shears, clamps, hypodermic syringes 
and needles, wax heater, cannulas and sticking 
knives, scalpels, instrument trays, antiseptic con- 
tainers, funnels, graduates, pipettes, detibrinating 
forks, porcelain containers for serum and virus 
blood, apparatus for separating out fibrin and clot, 
and bottles for storing and shipping. 

Grouped around this essential unit may be a 
multitude of accessories, or the unit itself may be 
multiplied so as to provide for production on a 
large scale. Facilities for butchering, for cooling 
carcasses, for rendering virus pig carcasses, for 
handling virus in separate rooms, for keeping 
susceptible pigs isolated, for dipping and isolating 
new arrivals, for bacteriological work, for packing 
and mailing products, and for exposing serum and 



82 HOG CHOLERA 

virus pigs to calves so as to guard against foot- 
and-mouth disease, are just a few of the acces- 
sories that circumstance must include or elimin- 
ate. 

Further detail in regard to equipment cannot be 
profitably discussed here. In all these things sim- 
plicity, cleanliness, convenience and low upkeep 
cost are the chief considerations. Good equip- 
ment invites clean operations, but in the last anal- 
ysis the quality of the finished product is not de- 
termined by equipment. A careless operator Avill 
contaminate serum in spite of every convenience ; 
a careful one will produce clean products under 
adverse working conditions. 

Principle governing serum production. When 
a hog contracts cholera and recovers, or when it 
receives simultaneously hog cholera virus and 
protective serum, it is thereafter immune to the 
disease. The body cells, in self-defense, have elab- 
orated substances, termed antibodies, which neu- 
tralize the effects of all hog cholera virus subse- 
quently introduced into the system. In the ordi- 
nary immune hog these antibodies protect against 
any quantity of cholera virus to which the animal 
may be exposed, but they do not exist in sufficient 
concentration so that the blood may be used to 
protect other animals. Antibody elaboration 
must be further stimulated, and this is done by 
giving the immune an enormous intravenous dose 



PEEPAKATION OF ANTI-HOG-CHOLEEA SERUM 83 

of virulent hog cholera blood. A slight reaction 
follows, and in the course of a few days the im- 
mune becomes a hyperimmune and comparatively 
small doses of its blood will protect other hogs ex- 
posed to cholera. 

We are now ready to consider in some detail the 
various steps required in preparing anti-hog-chol- 
era serum. In all these it is a principle that the 
operating room shall be clean and free from dust, 
that the floor shall be dampened, that the operator 
shall wear clean clothing and that his hands shall 
be scrupulously clean. The hands must not touch 
the serum or virus blood, and all instruments and 
containers with which the blood comes in contact 
must be sterilized before use. Antiseptic solution 
should be applied by means of a gravity irrigator 
or some other device which prevents the hands 
from passing alternately between operating field 
and antiseptic container. Exact records of each 
operation must be kept, and each hog used must 
be identified with a number tag. 

Immunizing. Requirements. Two hypodermic 
syringes, one ten mil capacity or less, for virus, 
the other twenty mil capacity or more, for serum ; 
scrub-brush and antiseptic solution, also anti-hog- 
cholera serum and hog cholera virus each in a 
separate, covered receptacle. 

The pig is held by an assistant and the skin 
covering both armpits (or the inner region of both 



84 HOG CHOLERA 

hams) is tliorouglily scrubbed mth antiseptic so- 
lution. Then two mils of virus are injected into 
one armpit, and the required quantity of serum 
(about 35 mils for a 100 pound pig) is injected 
into the other. Deep injections are desirable. 

Following this treatment the pig undergoes a 
reaction beginning in about five days and lasting 
about a week, during which time a permanent im- 
munity to hog cholera is established. It is de- 
sirable to immunize prospective hypers as com- 
paratively young shoats and to delay h^^ering 
until they have attained a weight of at least two 
hundred pounds, as a long interval between the 
date of immunizing and that of hypering favors 
potent serum. In no instance should this interval 
be less than sixty days. 

The Virus Pig 

In order that the immune may receive addi- 
tional virus and become a hyper, a supply of virus 
must be procured. This is done by injecting sus- 
ceptible shoats with lethal doses of hog cholera 
virus and collecting their blood after they sicken 
with the disease. A virus pig should be in thrifty 
condition, weighing near one hundred pounds. It 
should not be heavily infested ^vith parasites. 
The dose of virus (about 2 mils) is injected in the 
same manner as has already been described, but 
no protective serum is given. 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 85 

Four or five days subsequent to injection the 
pig should show a temperature near 106° F., and 
a day or two later marked symptoms of hog chol- 
era should appear. As a very general guide it 
may be said that a virus pig is ready to bleed when 
it has carried a high temperature for about three 
days and when it has shown severe symptoms of 
hog cholera for about two days. A good strain of 
virus will bring this about in approximately seven 
days subsequent to the date of injection. The 
time required may be extended in certain individ- 
uals, but a virus that regularly requires more than 
eight days in which to ^ ' ripen '^ pigs for bleeding 
is not desirable for hypering. 

Bleeding the virus pig. When the sick pig is 
ready to bleed for virus it is taken to the labora- 
tory. In the preparation room the entire body 
is washed, and the animal is secured to a tilting 
operating table, revolving door or other device for 
securing it by the hind legs and suspending it 
head downward. The front legs are secured well 
apart and the snout tied backward, stretching the 
skin covering the throat. The throat and sternal 
region are then thoroughly lathered (an antiseptic 
soap is desirable), carefully shaved and rinsed, 
and an antiseptic solution is applied. If it is a 
male pig a clamp is attached to the prepuce to 
prevent dribbling of urine. Finally the entire 
body is covered with a cloth, previously dampened 



86 HOG CHOLERA 



^ 



in antiseptic solution, leaving only the throat ex- 
posed, and all is ready to draw the blood. 

An ordinary two-quart fruit jar, previously 
sterilized, is a good receptacle. The sticking may 
be done with a large cannula designed especially 
for the purpose, or with a narrow bladed knife. 
In case a knife is used the hand should be held 
low on the throat so that the blade passes directly 
upward, the back against the dorsal surface of the 
sternum. The blade should not leave the median 
line, but should be forced upward until it severs a 
carotid or the anterior aorta near the bifurcation. 
A free clean incision made in withdrawing the 
knife facilitates rapid and complete bleeding. A 
pig weighing one hundred pounds should yield 
about one thousand mils of blood. If pigs are 
killed too late, after they are very weak, the yield 
is greatly reduced. 

Handling the virus blood. Immediately after 
the blood is drawn it is defibrinated. This is done 
by closing the receptacle tightly and shaking it 
vigorously for a few moments. It is then marked 
for identification and placed in ice-water pending 
the time when the pig that yielded the blood can 
be autopsied. Assuming that the autopsy, which 
will be considered later, has been satisfactory, the 
next step is to separate out the fluid part of the 
blood, leaving the clot and fibrin behind. This is 
accomplished in various ways. Some use a cen- 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 87 

trifuge of which the essential part is an enclosed, 
revolving, perforated cylinder; others pour the 
contents of the jars directly into funnels into 
which one or more thicknesses of sterile gauze 
have been placed ; still others empty the jars into 
perforated funnels which fit into the tops of tall re- 
ceptacles into which the fluid drains, and near the 
bottom of which is a turncock for drawing it off. 
Formerly clot presses were used universally as a 
final means of extracting the last drop of blood 
from the fibrin and clot, but this practice is gradu- 
ally being abandoned. It increases the yield but 
little, and adds unnecessary debris to the blood, 
whether it is serum or virus. In all methods of 
handling the final act is to strain the blood through 
gauze, after which it is placed in storage bottles 
and refrigerated pending the time when it is re- 
quired for Iwpering. The blood of several virus 
pigs is mixed after autopsies have confirmed its 
fitness for use. 

This ^^hypering virus'' may be kept forty-eight 
hours or even longer, but it is best to use it after 
it has been refrigerated about one day. It is well 
to strain it a second time just before it is to be in- 
jected. Preservative is never added to hypering 
virus. 

The autopsy. The two essential requirements 
for a virus pig are that it shall show complete evi- 
dence that it was suffering mth acute hog cholera 



88 



HOG CHOLERA 



at the time it was killed, and that it shall be free 
of other infectious diseases which may be trans- 
mitted through its blood. The clinical history of 
the pig, and more especially the autopsy, enables 
us to select on this basis. If in addition to a clini- 




Plate 9. Post-mortem room where autopsies on virus pigs are 
held. Each pig must show marked lesions of acute hog cholera, 
and must be free from other infectious diseases. (Courtesy 
Pitman-Moore Biological Laboratories) 

cal history suggesting hog cholera a pig shows 
characteristic lesions of the disease, slight or se- 
vere, in two or more organs, we consider the first 
requirement satisfied. Generalized tuberculosis 
disqualifies, but slight and localized tubercular le- 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 89 

sions do not cause rejection. Here, we believe, a 
very rigid interpretation is advisable, and in all 
cases which admit doubt the pigs should be re- 
jected. 

Pigs that show enormously enlarged, dark, 
pulpy spleens as well as those that bleed scantily 
and yield very dark blood do not produce satisfac- 
tory virus. The tendency in both cases is for the 
blood to defibrinate imperfectly and when it is 
mixed with good virus the entire lot may be 
ruined. 

In the routine autopsy the skin, and all of the 
thoracic and abdominal viscera are examined, as 
well as the submaxillary and superficial inguinal 
lymph glands. In case of doubt, due to slight le- 
sions, the mucosa of the larynx and popliteal 
lymph nodes should be included. 

Disposal of carcass. Virus pig carcasses may 
be burned or rendered as circumstances direct. 

The Hyperimmune 

The immunes which are to be hyperimmunized 
and later yield serum should be carefully selected. 
The longer they have been immune to hog cholera, 
the better. They should be hearty feeders, in 
moderate flesh, and always strong and active. 
The ears should be moderately large, but thin and 
well veined, and the tail at least of average length 
so as to permit the required number of bleedings. 



90 HOG CHOLEBA 

A weight near two hundred pounds is desirable. 
The intradermal tuberculin test should be applied 
to prospective hypers, and all reactors rejected. 

Hypering. The immune is confined in a port- 
able crate and the snout is secured firmly, drawing 
the head to one side. Its weight is then obtained 
and recorded, and it is wheeled to the preparation 
room in the laboratory. The entire body is wet 
thoroughly and a cloth dampened in antiseptic so- 
lution is thrown over it, leaving only the head ex- 
posed. One of the ears is lathered, shaved, rinsed 
and washed in antiseptic solution and the hog, 
thus prepared, is wheeled to the hypering room to 
receive the required dose of virus. 

The hypering operation consists of injecting 
into an ear vein five mils of virus blood for each 
pound the hog weighs. The virus is placed in a 
graduated bottle which is closed mth a rubber 
stopper, perforated in two places. Through one 
opening is passed a curved nickeled tube which, ex- 
tending to the bottom of the bottle, serves as an 
outlet for the virus when air pressure is applied ; 
through the other is passed a shorter tube extend- 
ing just through the stopper and through which 
air is pumped to produce pressure. Both are ex- 
tended with rubber tubing, the intake being thus 
connected with a tank containing compressed air, 
and the outlet terminating in a slip fitting for the 
hypodermic needle which is to be introduced into 



PKEPARATION OF ANTI-HOG-CHOLERA SERUM 91 

the ear vein. On this outlet tube is a pinch-cock 
to control the flow of virus. The bottle is filled 
mth virus, the stopper is forced down tightly with 




Plate 10. A close view showing the hypering process. 
A 200 pound cholera immune hog receives 1000 mils 
of virus in the ear vein. In ten days the animal is 
ready to bleed for protective serum. New York State 
Veterinary College at Cornell University 



92 HOG CHOLERA 

a screw clamp, enough virus is passed tlirough the 
system to ehminate danger from air bubbles, the 
pinch-cock is closed, and all is ready to make the 
injection. 

The vein into which the needle must be intro- 
duced usually conforms roughly to the contour 
of the outer margin of the ear, and is about one 
inch removed from it. A spring clamp is ap- 
plied near the base of the ear, thus compressing 
this vein and rendering it plainly visible. The 
ear is drawn taut with the left hand, and with 
the right the needle is thrust quickly into the vein, 
passed rapidly along its course about two inches, 
and secured in position with the clamp which is 
no longer needed to compress the vein at the base 
of the ear. If the needle is properly in place there 
will be a backward flow of blood through it. With- 
out a moment's delay it is now necessary to con- 
nect the needle with the supply of virus under 
pressure, and to open the pinch-clock allomng the 
virus to flow into the circulation. Otherwise the 
hog's blood may clot in the needle rendering the 
injection impossible. When the flow of virus is 
established, one must see that the needle is re- 
tained in place until the required quantity, al- 
ready determined, has been injected. This will 
require from four to thirty minutes, the time be- 
ing governed by the degree of pressure applied, 
by the size of the needle and the accuracy with 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 93 

which it has been placed in the vein, as well as by 
individual differences in hogs that are not well 
understood. When the required quantity of virus 
has been injected, the pinch-cock is closed, the 
needle is withdrawn, and the hog is wheeled away 
and released. 

This describes the hypering operation in its 
simplest form with everything favoring the oper- 
ator. Volumes could be written about the at- 
tempts that end in failure. Practice is important, 
but a natural surgical touch amounting almost to 
instinct is required of the expert operator, and 
even he may experience unexplainable lapses in 
the execution of his technique. However, most of 
the annoyances experienced may be overcome, and 
it seems desirable to include a few suggestions 
which may aid the beginner in his work. 

At first select hypers with ear veins straight 
and prominent; later it will be possible to hyper 
practically all subjects : begin the operation soon 
after the ear has been shaved ; otherwise the vein 
may recede and be very difficult to distend so that 
the needle may enter it : use a needle with a per- 
fect point ; a dull one will roll the vein under it : 
Hold the ear out straight ; otherwise the skin will 
be relaxed and the vein will be unnecessarily tor- 
tuous : after the needle has entered the vein do not 
release it until it is clamped firmly in position; 
the nub may drop carrying the point upward and 



94 HOG CHOLERA 

causing it to prick through the wall so that virus 
will escape from the vein and accumulate in the 
surrounding tissues when it is applied under pres- 
sure : if the needle tends to pucker the skin at the 
point of entrance, dampen both needle and skin 
(an atomizer containing alcohol is convenient for 
this purpose). In inserting the needle hold the 
index finger of the right hand well toward the 
point, between the ear and the needle; it is im- 
possible to guide a needle when it is grasped at 
the nub only: if when pressure is applied virus 
is seen to escape from the vein and accumulate in 
the surrounding tissues, release the pressure at 
once ; otherwise all chance of entering the vein in 
subsequent trials Avill be destroyed. 

Before inserting the needle some operators 
connect it directly to the rubber tubing containing 
the virus under pressure, thus obviating annoy- 
ance incident to blood clotting in the needle or to 
accidental breaks in the slip connection due to 
struggling on the part of the hog. When this 
technique is employed one must depend largely on 
his sense of touch to determine when the needle 
is in position, for backward flow of blood cannot 
be observed. In case of doubt as to whether the 
needle has entered the vein, one may compress the 
tubing between the pinch-cock and the needle, at 
the same time observing whether the virus thus 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 95 

forced out follows the course of the vein or is dis- 
tributed in adjacent tissues. 

Occasionally one encounters a fleshy-eared hog 
exhibiting no ear vein which is visible to the naked 
eye in ordinary light. Subjects of this kind may 
usually be hypered by darkening the room and 
holding an electric light bulb directly under the 
ear. Small, deeply covered veins are thus ren- 
dered plainly visible, and hypering is accom- 
plished with surprising ease. 

Dangers and accidents due to hypering. The 
ordinary immune hog will tolerate, without inci- 
dent, intravenous injection of five mils of virus 
per pound body weight. Usually there is no evi- 
dence of pain or distress, and the animal lies 
quietly while the dose is being administered. In 
exceptional cases, however, sudden death occurs. 
It is a curious fact that if distress is to appear, 
it becomes evident before the first half of the dose 
enters the circulation. Thus it is not quantity 
alone that kills. Other factors may contribute, 
but the principal one seems to be failure of nerv- 
ous control over capillary contraction. The 
capillary walls fail to adjust themselves to the 
increased pressure, and as a consequence distend 
and rupture. Usually the lungs alone bear evi- 
dence of this fact, as they contain the first set of 
capillaries through which the foreign blood must 



96 HOG CHOLERA 

pass, but occasionally the effect is observed in the 
skin. Severe and general congestion, interspersed 
with areas revealing slight or extensive hemor- 
rhage, are the usual changes observed in the 
lungs. 

Prevention of sudden death resulting from hy- 
pering is not always possible. Fatalities occur 
much less frequently if the virus used is first 
thoroughly cooled. Even ordinary refrigerator 
temperatures are not objectionable. As a second 
precaution a close watch should be kept on the hog 
during the process of hj^pering, though it is not 
always possible to distinguish between struggles 
due to fright and perversity and those due to 
genuine distress. Real danger is marked by a 
sudden inspiratory gasp or rapidly developing 
dyspnea, especially when these symptoms are ac- 
companied by violent struggling and nervous 
symptoms such as twitching of the snout or eye- 
lids and protrusion or shuttling of the eyeballs. 
If distress is not severe the flow of virus may be 
checked momentarily and then allowed to con- 
tinue slow^ly, but as a rule it is best to release the 
hog and take no further chances. Usually in sub- 
sequent trials these hogs will tolerate h^^ering 
without incident. 

Sometimes it is not until the hog is released 
from the crate that we observe symptoms. Vomit- 
ing occurs somewhat frequently at this time but 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 97 

it is of no particular consequence. Great prostra- 
tion and severe dyspnea are the symptoms which 
suggest impending death, especially when foam 
colored with blood exudes from the mouth or nos- 
trils. Hogs suffering thus should be kept cool, 
their heads should be elevated, and they should 
not be subjected to unnecessary handling. Some 
will recover spontaneously. In fatal cases coma 
and shallow breathing precede death. We have 
tried hypodermic doses of strychnin under such 
conditions, but while temporary relief is afforded 
the treatment seems merely to delay death rather 
than to prevent it. 

Fatalities sometimes occur w^hen air is pumped 
into the vein. These may be avoided by forcing 
the outlet tube completely to the bottom of the 
bottle, and by allowing, previous to each opera- 
tion, a quantity of virus to pass through the out- 
let sufficient to carrj^ away bubbles that may be 
accumulated in the rubber tube. Air in the vein 
does not always cause death, but the risk is great, 
and avoidable. 

Deaths from hog cholera as a result of hypering 
are practically unknown, except in hogs that have 
been purchased without a clear history of having 
been properly immunized. 

During the interval between the date of hyper- 
ing and that of the first bleeding for serum, about 
ten days, careful observations of the hyper are 



98 HOG CHOLERA 

necessary. The points to be determined are 
whether the hog has been vigorous and healthy, 
and whether this condition still prevails at bleed- 
ing time. Temperature readings, clinical obser- 
vations and comparative weights are the sources 
of information, each being employed as circum- 
stances direct. The average hjiper shows a mod- 
erate and transitory fluctuation of temperature 
immediately following the dose of virus, and he 
may eat indifferently for a day or two, but as a 
rule his appetite is unimpaired, and he continues 
to gain in weight about a pound per day. If a 
hog's appetite has been greedy during the last 
seven days preceding the date of bleeding ; if there 
has been no loss in weight or outward evidence of 
sickness ; and if the temperature is normal when 
bleeding time arrives, we consider the animal a 
fit subject to produce serum. 

Bleeding for serum. The hog is confined in a 
portable crate and wheeled to the preparation 
room. Bleeding is to take place from the tail 
which now requires thorough mechanical cleans- 
ing. Warm water and antiseptic soap are applied 
freely and a stiff scrub-brush is used to work up 
a lather. After several minutes of scrubbing, the 
tail, and a circular area surrounding its attach- 
ment, are carefully shaved. The body of the ani- 
mal is then wet to settle dust that may be con- 
tained in its coat, and a cloth dampened in anti- 




Plate 11. Bleeding unit, and hog prepared for bleeding, but 
still uncovered. The fruit jar and breeding horn are 
clamped together and sterilized as a unit. The rubber 
cap is removed from the mouth of the horn immediately 
before the latter is applied to the hog's tail. New York 
State Veterinary College at Cornell University 



99 



100 HOG CHOLERA 

septic solution and containing a hole through 
which the tail protrudes, is thrown over the body. 
Thus prepared, the animal is ready for the bleed- 
ing room. 

Bleeding is accomplished with vacuum which 
hastens the process and retards coagulation. The 
essential bleeding unit consists of a curved metal 
horn, one end armed with a fitting which receives 
the mouth of a two-quart fruit jar, forming an air 
tight joint, and the other consisting of a round 
or oval-shaped opening presenting a moderately 
broad surface to be pressed firmly against the skin 
surrounding the tail, which member the horn en- 
closes. Communicating with the interior of the 
unit is a tube which, continued with rubber tubing, 
connects with a pipe leading to a vacuum tank. 
Somewhere in the line is a turncock so situated 
that vacuum may be employed or released at will, 
and between this and the bleeding unit is an intake 
valve fitted with a small cup containing carbolized 
cotton through Avhich air must pass to release the 
vacuum remaining in the unit when bleeding is 
completed and the turncock is closed, severing 
connection with the vacuum tank. A vacuum indi- 
cator is inserted in the line between the tank and 
the turncock. 

The operator grasps the tail, disinfects it thor- 
oughly, and dries it with alcohol. Then with 
shears designed especially for the purpose an inch 




Plate 12. Bleeding for F'^riim. Vacuum is applied through the 
rubber tube, and the blood flows into the jar, 1000 mils of 
blood can be drawn in about 8 minutes. New York State 
Veterinary College at Cornell University 



101 



102 HOG CHOLERA 

or more is clipped off the end, and the part re- 
maining is guided into the bleeding horn, which 
is forced tightly against the body. When vacuum 
is applied the contact is rendered air-tight, and 
blood streams rapidly from the severed tail. 
Moderate and uniform traction should be applied 
during the process of bleeding. When the desired 
quantity of blood has been drawn, the turncock 
is closed, the vacuum remaining in the unit is re- 
leased through the intake valve already described, 
and the tail is ligated near the end or the raw sur- 
face is seared to prevent further hemorrhage. 
It is well to cover all the shaved surfaces with 
ointment thus preventing chapping of the skin 
which may render subsequent bleedings difficult. 
Bleeding technique is a determining factor as 
far as cleanliness of the serum is concerned, and 
too much importance cannot be attached to it. 
Thorough mechanical cleansing of the tail and 
surrounding parts is a first essential. Before the 
razor is used, warm water and soap should be 
applied vigorously for some time, thus softening 
the hair and removing all scurf. Disinfecting the 
tail previous to bleeding should never be alloAved 
to degenerate into a mere perfunctory process. 
During the bleeding operation every effort should 
be made to prevent the vacuum from being broken, 
for this admits a stream of air which may be con- 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 103 

taminated, and which, in any event, is sure to 
hasten coagulation of the blood. 

We have not found dehbrinating during the 
bleeding process either necessary or desirable. If 
it is done by shaking the jar into which the blood 
is flowing, it causes the hog to struggle, thus re- 
tarding the bleeding process and rendering break- 
ing of the vacuum imminent ; and if it is done by 
any device which renders shaking unnecessary 
during the time the blood is being drawn, com- 
plete defibrination can be brought about only by 
shaking the jar after bleeding is discontinued. 
On the other hand, if the hog is allowed to lie per- 
fectly quiet, and if moderate and steady traction 
is applied after the vacuum is established, bleed- 
ing takes place rapidly, and almost without excep- 
tion perfect defibrination will be secured if the 
blood is shaken immediately after bleeding is com- 
pleted. Individuals differ, but the average hog 
bleeds best under about fifteen inches of vacuum. 
Contrary to what might be expected, a more per- 
fect vacuum than this usually tends to retard 
bleeding rather than to hasten it. 

Each hyper is bled once each week during a 
series of from two to four bleedings, after which 
it may be rehypered at any time. In rehypering 
only 21/2 Mills of virus per pound body weight are 
required. Following this second dose of virus a 



104 HOG CHOLEKA 

like series of bleedings takes place, the first oc- 
curring from seven to ten days subsequent to re- 
hypering. The final bleeding takes place from the 
throat in exactly the same manner in which virus 
pigs are bled, except that the blood is usually 
drawn into a deep porcelain receptacle, and de- 
fibrinated by whipping it with a large fork. If 
inspection does not disqualify, the blood of the 
hyper, which has been kept separate throughout 
the two series of bleedings, is admitted to test, 
and the carcass is placed on the market. 

Handling serum blood. Immediately after the 
bleeding process is completed the jar containing 
the blood is sealed, and then shaken for a few 
moments to whip out the fibrin. When this proc- 
ess is completed the jar is placed in ice-water. 
Later, the fibrin is separated from the fluid by 
exactly the same process that is employed mth 
virus blood. Here again, the clot-press is detri- 
mental because it adds superfluous debris to the 
serum and causes it to be exposed to the air un- 
necessarily. After the defibrinated blood is 
strained there is added to it, as a preservative, 10 
mils of 5 per cent aqueous solution of carbolic 
acid for each 90 mils of blood. The product is 
then placed in storage bottles, labeled, and re- 
frigerated pending the time when enough has 
accumulated for a test. 

In laboratories which do not clarify the serum, 



« 



PREPAEATION OF ANTI-HOG-CHOLERA SERUM 105 

the blood of each hyper is stored separately so 
that if the animal should show on autopsy general- 
ized tuberculosis or other disqualifying disease, 
the blood may be discarded. Local conditions 
must govern these details. In our own laboratory 
where it is possible to purchase hypers which 
have not followed cattle and have not been fed raw 
creamery products, we always mix bleedings, in 
spite of the fact that we do not clarify the serum. 
We have never had a hyper show generalized 
tuberculosis, and in the few instances in which 
we have found the disease localized, we have used 
a guinea-pig test to determine the fitness of the 
serum for market. We believe this test has a 
wider application than is now accorded it. 

FINAL PROCESSES IN SERUM PRODUCTION 

Testing". Irrespective of detail in preparation, 
the final requirement is that the finished product 
shall pass a test proving its protective potency 
under carefully controlled conditions. For this 
purpose there is drawn a sample from a mixed lot 
consisting usually of about 100,000 mils of serum. 
Seven pigs weighing between 45 and 90 pounds 
each are selected for the official Bureau of Animal 
Industry test. Temperatures must be normal and 
all pigs in good physical condition at the time the 
test begins. Each pig is given 2 mils of hog 
cholera virus, five of them receiving in addition, 



106 HOG CHOLERA 

and at the same time, 20 mils each of the sample 
of serum to be tested. The other two receive no 
serum, but are employed as controls to determine 
the virulence of the virus. Daily observations are 
made and temperatures are recorded as required, 
preferably once a day. The essential require- 
ments for a satisfactory test are that both pigs 
which receive virus only shall sicken during the 
test period (21 days) and that at least one of them 
shall sicken between the fourth and seventh days 
subsequent to injection, and shall before the fif- 
teenth day suffer from hog cholera in a degree 
sufficient to cause death. As an additional con- 
dition, no more than one of the pigs that receive 
serum and virus shall show visible illness, and in 
case one should sicken it must be completely re- 
covered before the twenty-first day following the 
beginning of the test. 

Bureau of Animal Industry regulations govern- 
ing the interpretation of tests will be found in the 
Appendix. In general, tests are classified accord- 
ing to results as * ^ satisfactory, ' ' *^ unsatisfac- 
tory^' or *^no test,'' the latter giving indefinite 
results. The satisfactory test has already been 
described; the unsatisfactory test is usually re- 
ferred to impotent or contaminated serum; re- 
tests are indicated when the serum-treated pigs 
or more than one of the virus pigs sicken before 
the fourth day, when the control pigs do not sicken 




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108 HOG CHOLERA 

as is required in a satisfactory test, or when inter- 
current disease or accident intervenes. 

Too much stress cannot be placed on the test, 
for it is here that all technique leading up to com- 
pletion of the finished product receives its final 
confirmation. Careful observations are necessary 
as well as strict interpretations which mthhold 
from use all doubtful serum. Regulations are a 
valuable guide, but they themselves require skill- 
ful interpretation, and no exact rules can be laid 
do\^^i which ^^ill serve their intended purpose 
under all circumstances. Is the serum highly po- 
tent? Is it free from organisms that will injure 
hogs into w^hich it is injected? When test con- 
ditions answer both questions definitely in the 
affirmative, the serum is fit for use. If doubt re- 
mains it may be retested, and if it has failed to 
protect healthy pigs in average condition it should 
be discarded. 

In our own work we greatly prefer an eight pig 
test in which two of the serum pigs receive 10 
mils each of serum, two 15 mils each, and two 
others 20 mils each. We believe that these low 
doses give much more complete information re- 
garding the potency of the product, thus allomng 
a greater margin of safety and adding to the con- 
fidence mth which it may be used in the field. 
Out of the last 45 tests conducted in this manner 
37 have passed without incident, intercurrent dis- 



PEEPAKATION" OF ANTI-HOG-CHOLERA SERUM 109 

ease (heavy ascaris infestation) necessitated 
three retests which were satisfactory, one 10 mil 
serum pig died in each of two, one 15 mil pig died 
in one, and two were wholly unsatisfactory due to 
low potency. The test pigs ranged in weight be- 
tween 27 and 105 pounds, the average being 59. 

It is of advantage to select test pigs from herds 
in which no immunizing has been done and in 
which hog cholera has not appeared in recent 
years. It is well if all pigs in a single test can 
be litter mates. The pigs should not be subjected 
to long hauls just before they go on test, and dur- 
ing the test great care is necessary to prevent 
overfeeding of the serum pigs at the time when 
their reaction begins, which is about the time the 
virus pigs refuse feed entirely. As a routine 
measure it is a good plan to reduce the feed one- 
third or one-half on the morning of the fourth day 
of test, and to feed subsequently so that the serum 
pigs are kept just a little hungry. 

It is interesting and highly instructive to ob- 
serve the progress of a series of tests, and we 
know that some field workers would be more cau- 
tious in their vaccinating if this experience could 
be theirs. It is in this manner that we see results 
of the battle between protective and destructive 
forces, and are brought to realize how easy it is 
for some disturbing factor to turn the tide in 
favor of destruction. The virus pigs usually show 



110 HOG CHOLERA 

a temperature near 106° F. on the fourth or fifth 
day of the test, and this high level is maintained 
several days. Other symptoms of hog cholera ap- 
pear a day or two after the temperature curve 
starts upward. The pigs which receive protective 
serum in addition to virus also undergo a reaction, 
which is slightly delayed and very mild as com- 
pared to that observed in the virus pigs. In some 
instances no temperature reaction is discernible, 
but usually readings reach a point between 104° 
and 105° F., considerable fluctuation between nor- 
mal and this level being observed. As a rule the 
casual observer would detect no evidence of a 
physical reaction, but not infrequently the appe- 
tite lags just perceptibly for two or three days 
and in white pigs a slight flush may be observed 
in the skin. On the whole, all evidence of reaction 
has usually disappeared from the serum pigs be- 
fore the tenth day of the test. 

According to Bureau of Animal Industry regu- 
lations, serum which protects in doses required in 
their official test is suitable for use in the field 
under a dosage label as follows : 

Sucking pigs 20 mils 

Pigs, 20 to 40 pounds 30 mils 

Pigs, 40 to 90 pounds 35 mils 

Pigs, 90 to 120 pounds 45 mils 

Pigs, 120 to 150 pounds 55 mils 

Hogs, 150 to 180 pounds 65 mils 

Hogs, 180 pounds and over 75 mils 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 111 

Bottling and labeling. After a lot of serum 
has passed a satisfactory test it remains to place 
it in bottles of suitable size for shipping. In 
large laboratories this is done with machines de- 
sigTied especially for the purpose ; in smaller ones 
it is done by placing the serum in a large covered 
container drained by a tubular outlet on which is 
fitted a few inches of rubber tubing. This tubing 
terminates in a small umbrella-shaped aluminum 
device, the serum flowing through the part repre- 
senting the handle, and the bottle being protected 
from dust during the filling process by the part 
representing the cover. All bottles intended for 
shipping are sealed and placed in the refrigerator 
until they are needed. 

A label should be placed on every bottle of se- 
rum shipped, and should include : 

1. Release tag and license number if the labora- 
tory is being operated under federal license. 

2. Name and address of manufacturing firm or 
institution. 

3. Dosage table. 

4. Identification mark, which will enable the 
•manufacturer to trace the exact history of any 
bottle of serum. 

5. Return date, or latest date on which the se- 
rum may safely be used. 

6. Brief directions for use and caution regard- 
ing methods of preservation. 



112 HOG CHOLERA 

The finished product. It has already been 
shoAvii that all serum sent out is, or should be, 
subjected to carefully controlled tests in which it 
is required to protect laboratory pigs in much 
smaller doses than would be administered to like 
animals in the field. The protective defibrinated 
blood, called anti-hog-cholera serum, is the basic 
preparation from which all the more or less re- 
fined products now on the market take origin, and 
when it is prepared with careful technique it is in 
the original state a highly effective and safe im- 
munizing agent. It may or may not be sterile. 

Clear serum is ''bloody serum ^' minus blood 
corpuscles. It is prepared from the protective 
defibrinated blood by various combinations of 
processes which, individually considered, include 
precipitation of the red blood corpuscles with 
navy bean extract, centrifuging, and filtering 
through various materials. Heat, 60° C, for one- 
half hour, is applied, which kills some contaminat- 
ing organisms that may be present. An impres- 
sion seems to prevail that all clear serum is sterile, 
but this is not true, for it is not necessarily sub- 
jected to temperatures or other treatment which' 
will kill or remove all living bacteria. 

The comparative merits of clear and "bloody*' 
serum are the subject of much controversy, but as 
is true of other things of like nature, individual 
methods are the deciding factor. Clear serum, 



PREPAKATIOISr OF ANTI-HOG-CHOLERA SERUM 113 

if not subsequently diluted may be administered 
in somewhat smaller doses than can ^^ bloody'' 
serum, it is free from extraneous matter which 
has no immunizing value, and all other things 
being equal it is more likely to be sterile. On the 
other hand it usually becomes cloudy on standing, 
its keeping qualities and continued potency after 
heating, so often emphasized, are yet to be fully 
established, and it is more expensive than the 
^'bloody" serum. ^'Bloody" serum contains cor- 
puscles which are of no value in immunizing, and, 
like the clear serum, if it is not carefully prepared 
it may also contain excessive numbers of bac- 
teria. On the other hand it is not subjected to 
complicated processes which invite error in tech- 
nique, and it can be prepared much more cheaply, 
per immunizing unit, than clear serum. 

Disregarding entirely the form of the finished 
product, the test, conscientiously applied and 
skillfully interpreted, is the swine breeder's guar- 
antee of safety to his herd. Thus either clear or 
^'bloody" serum, carefully prepared, is a safe and 
effective immunizing agent; neither, carelessly 
prepared, will produce the results the breeder and 
his veterinarian have a right to expect. 

The relative merits of tail-bled and carotid-bled 
serum have also been the subject of much absurd 
controversy, for no scientific evidence has ever 
been submitted to prove one product different 



114 HOG CHOLERA 

from, or superior to, the other. Carotid-bled se- 
rum is a mere ^^ talking point.'' Some laborato- 
ries situated near stockyards can produce it more 
cheaply than they can produce the tail-bled prod- 
uct, and this fact, rather than considerations 
based on the quality of the product, explains their 
preference for carotid-bled serum. Both products 
pass like tests before being released for use. 

The keeping qualities of anti-hog-cholera 
semm vary with different lots, and with various 
methods of preparing and storing. Bureau of 
Animal Industry regulations place the expiration 
date at two years from the time the first bleeding 
in a particular lot takes place, and subject to satis- 
factory retest at the end of two years, another 
year may be added. Our own preference is for a 
shorter period, for in one or two instances we 
have knoAvn serum to fall away in potency before 
it was two years old. 

Serum should always be stored in a dark, cool 
place. According to a limited number of tests 
conducted by Kernkampf, freezing does not in- 
jure it, but temperatures below the freezing point 
are not desirable. A temperature between 40° 
and 55° F. seems to be most favorable. After the 
seal on a bottle has been broken and a portion of 
the serum removed, the remainder should be used 
in the course of a few days, or discarded. It is 
always well to open the bottle out of doors, if all 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 115 

the serum contained in it is not required for im- 
mediate use. 

The scope and purpose of this book do not allow 
further detail which might profitably be included 
in a more inclusive text. In leaving the subject 
of serum production, let us emphasize again a 
few essentials which make for clean, potent serum. 
These include strong vigorous hypers that have 
been immune to hog cholera a long time before 
being hypered; a highly virulent strain of virus 
that will ^' ripen'' pigs to kill in seven days, or 
less; scrupulous cleanliness and strict antisepsis 
in all operations; rapid cooling of all blood im- 
mediately after it is drawn ; no unnecessary han- 
dling or exposure of serum during the process of 
defibrinating and straining; and finally, careful 
observation of tests, with positive exclusion of 
doubtful serum. 

Hog Cholera Virus 

Hog cholera virus, called by the trade ** simul- 
taneous virus'' because it is used in the field in 
conjunction with protective serum, is produced 
by giving shoats doses of virus (usually 2 mils 
each), allomng them to sicken, and drawing their 
blood while the disease is at its height. This blood 
is handled in exactly the same manner as hyper- 
ing virus, differing from this latter product only 
in that there is added to it as a preservative, 5 



116 HOG CHOLERA 

mils of 5 per cent aqueous solution of carbolic acid 
for each 95 mils of blood. The pigs used to pro- 
duce simultaneous virus must meet the same es- 
sential requirements as are met by those used to 
produce hypering virus; that is, they must show 
ample evidence that they are suffering with acute 
hog cholera at the time they are bled, and they 
must be free of all other infectious diseases trans- 
missible through their blood. 

Hog cholera virus is sometimes heated at 50° C. 
for twelve hours before being sent out, in which 
case a virulence test is necessary before it can 
be released for field use. In our own work we 
greatly prefer unheated virus. 

Keeping qualities. Like protective serum, hog 
cholera virus must be kept in a dark, cool place. 
Bureau of Animal Industry regulations allow it 
to be used not more than sixty days subsequent to 
the date of dramng, but wherever a thirty-day 
limit is practicable, we believe it is safer. There 
are times when an inactive virus may result in as 
heavy losses as are sometimes charged to impo- 
tent serum. 

Labeling". The virus label should include: 

1. Release tag and license number if the labora- 
tory is operated under federal license. 

2. Name and address of manufacturing firm or 
institution. 

3. Dosage table. 



PREPARATION OF ANTI-HOG-CHOLERA SERUM 117 

4. Identification mark, enabling the manufac- 
turer to trace the exact history of any bottle of 
virus. 

5. Eeturn date, or latest date on which the virus 
may safely be used. 

6. Directions for storing. 

7. Brief directions for using, and cautions to 
be observed in destroying unused virus. 

Hog cholera virus is dangerous material. One- 
half mil or even less will readily kill an ordinary 
susceptible hog if protective serum is not admin- 
istered in conjunction with it. Thus hogs given 
simultaneous treatment in the field actually re- 
ceive, as a routine measure, a lethal dose of virus. 
It is really remarkable that this practice results 
in so little trouble, but potential danger, slight 
though it is, exists whenever virus is used, and 
this fact should be well understood both by the 
veterinarian and his client. Under no circum- 
stances should virus be used by untrained men. 



CHAPTER VIII 

METHODS OF USING ANTI-HOG-CHOLEKA SEKUM 

Confining the animals. We will consider first 
methods of confining the animals to be treated. 
To one unaccustomed to handling hogs the task 
of confining and vaccinating a large herd of swine 
seems formidable, and not infrequently the diffi- 
culties presented, although largely imaginary, 
have led to costly neglect or procrastination. 
Chasing hogs to catch them is usually futile, it is 
time consuming, and if double treatment is to be 
applied, or if the animals are fat, the practice is 
positively dangerous. Ingenuity is required, and 
the veterinarian who can use the help and ma- 
terials at hand to best advantage, enabling him to 
vaccinate a herd quietly and rapidly, and without 
exciting the animals, gains much in the confidence 
of his clients. 

If the time that vaccinating is to be done is ] 
knoAvn to veterinarian and client the latter should i 
tempt the animals into pens or small enclosures 
with feed and fasten them in securely. Bedding 
should be provided so that the hogs will be clean 
and dry. In cases of emergency, where this ad- 

118 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 119 

vance knowledge is lacking hurdles should be used 
to crowd the animals into the corner of a yard or 




Plate 14. Injecting anti-hog-cholera serum in the ham 

pasture. In all cases in which fences are insecure 
it is important to mark each animal at the time it 
is vaccinated, so that if treated and untreated ones 



120 



HOG CHOLERA 



should accidentally get together identification will 
still be possible. Paint, chalk, bluing or tincture 
of iodin are convenient for this purpose, or if a 




Plate 15. Method of holding shoat for injecting 
serum in axillary space 

permanent mark is desired, the ear may be 
notched. 

Assuming that the animals are fastened in small 
pens when the veterinarian arrives, confinement 
of the individual during the process of immuniza- 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 121 

tion is the next step. As a site of injection, one 
may select the armpit, medial surface of the thigh, 
or the area immediately behind the ear. The site 




I'late 16. An improvised method of holding shoats for 
immunizing. Injecting serum in axillary space 

chosen, the size of the animal and individual pref- 
erences determine the method of holding. If the 
site is to be the medial surface of the thigh, any 



122 HOG CHOLERA 

pig weighing less than sixty pounds may be seized 
by the hind legs and held with the head suspended, 
belly toward the operator. If the armpit is 
chosen the pig is suspended by the front legs 
which are drawn well apart. 

Shoats weighing more than sixty pounds are 
confined in a variety of ways. Sometimes they 
are thrown and held on their backs; sometimes 
two men suspend them by their hind legs ; at other 
times it is convenient to incline a V-shaped hog 
trough against a fence so that it forms an angle of 
about 45 degrees with the ground. Into this the 
shoats are placed on their backs, heads do^\mward, 
and their snouts are allowed to slide under a cleat 
which extends across it. Perhaps the most serv- 
iceable method of handling animals of this size is 
to seize them by the front legs and set them on 
their haunches with their backs drawn firmly 
against the legs and body of the man holding 
them. In this position they are quite helpless and 
they are easily held as their weight rests entirely 
on the ground. Shoats thus confined are injected 
in the armpit. 

In throwing larger hogs that are to be held on 
their backs for treatment it is well to seize them 
by the front leg on the nearest side. A common 
mistake is to reach under them for the off foreleg. 
Another convenient and surprisingly easy method 
of throwing is to seize the tail with the right hand 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 123 

and the left hind leg with the left, pulling down- 
ward and to the right on the tail, upward and to 
the left on the leg. Like the double half -hitch in 
throwing a bull, this method of throwing hogs is 
effective, but its manner of action is a mystery. 

Large hogs are seldom thrown but are confined 
either by means of a noosed rope which is placed 
well back in the mouth and tightened around the 
snout, or with one of the many types of hog-hold- 




Plate 17, Convenient hog holder made from i/o inch gas pipe 
and flexible clothes wire. It may be disjointed in the 
middle for convenience in carrying 

ers. In case a snout-rope is used it should be 
either i/4 or % inches in diameter, and about fif- 
teen feet long. An eye about % inches in diame- 
ter is braided in one end, and through this the 
other end of the rope is passed to make a running 
noose. Directly around the rope forming the 
noose is braided a jerk-rope about a foot long. 
This device renders it possible to release a hog 
instantly, and saves time, for if it is not used re- 
leasing the animal sometimes is as difficult as 
confining it. A large rope tied in any manner to 



124 



HOG CHOLEKA 



form a running noose is clumsy to liandle, and 
allows a great many animals to escape. 

There is a great knack in noosing the snout of 
a large hog. Assuming that a person is right- 




1 



Plate IS. Method of preparing snout rope for confin- 
ing large hogs. The short ''jerk-rope" renders it 
possible to release the hog instantljv ^/i or % inch 
Manila rope is used 

handed he should stand near the center of the pen 
and start the animal moving around it to the left, 
at the same time seeking a position at the hog's 
left shoulder. Holding in readiness a short sec- 
tion of the noose, and at the same time crowding 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 125 

the hog suddenly and forcibly against the side of 
the pen with the right leg, one takes advantage 
of the fact that the animal opens its mouth to 
squeal or champ its teeth when its progress is thus 
momentarily arrested. The noose is slipped into 
the mouth, drawn backward quickly, and tightened 



1^^^^. 







^ i. 




^^^gp^^^^ 




■^^Jl 


.^/ 






1 






■wT 


" \ 





Plate 19. Method of noosing the snout of hog. The animal 
is forced suddenly against the gate with the right knee, 
the noose is thrust into the mouth, drawn behind the 
canine teeth and tightened 

around the snout. The free end of the rope is 
then secured and the animal is tapped on the snout 
to make it pull backward, for a hog mil not stand 
quietly unless the rope is tight. In this position 
the site of injection behind the ear is readily 
available. When a sow and sucking pigs are to 



126 HOG CHOLERA 

be immunized, the sow should be tied and injected 
first, and released only after the pigs have been 
vaccinated. 

Another method of confining large hogs is to 
connect two pens with a narrow, low chute, which 
can be closed at both ends. Into this a limited 
number of hogs are crowded tightly as they pass 
from one pen to the other, and the operator may 
reach over the side of the chute and inject the 
animals behind the ear. This involves some labor 
in preparation, but it is a rapid method of han- 
dling, and may be serviceable when a large num- 
ber of hogs are to be immunized. Quiet hogs may 
sometimes be injected without resorting to noose 
or holder as the operation is by no means painful. 

Methods of Using Serum 

Preventive vaccination against hog cholera in- 
volves the use of just two materials; anti-hog- 
cholera serum, which is protective in nature, and 
which is prepared from the blood of hogs that are 
hyperimmune to cholera; and hog cholera virus 
which is the defibrinated and preserved blood of 
pigs that are suffering with hog cholera at the 
time bleeding takes place. With these two ma- 
terials three methods of immunizing have been 
developed; serum alone, simultaneous (double, or 
serum-virus), and follow-up, which is a combina- 
tion of the two first-named methods. 



1 



I 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 127 

The practicing veterinarian is regularly re- 
quired to select the method best suited to the 
conditions he encounters, and he can handle hog 
cholera with maximum efficiency only when he 
judiciously chooses and employs the particular 
method indicated. The selection is based entirely 
on the effects produced by each method, just as we 
choose drugs on the basis of their action. When 
once these effects are well understood, the choice 
involves no great difficulties. 

Serum alone method. This consists of deep 
injection of the required quantity of serum. If 
the animals thus treated are not infected ^ with 
hog cholera immediately before or during the four 
weeks following serum administration the immu- 
nity conferred may, with rare exceptions, be de- 
pended on four weeks. In many individuals it 
lasts much longer. Swine more than twelve weeks 
old that receive serum alone and are infected with 
cholera immediately before immunization, or dur- 
ing the three or four weeks following, are there- 
after permanently immune. The effect on pigs 
less than twelve weeks old is still a matter of con- 
troversy, but at present we are not safe in depend- 

^ Much misunderstanding has arisen because of the loose use 
of the terms ''infected" and ''exposed." The first term implies 
that hog cholera virus sufficient to produce the disease has actually 
entered the system ; the second implies that the animal has been 
in close contact with virus from any source, but infection may 
or may not have taken place. Hogs given serum alone and in- 
fected with hog cholera acquire a permanent immunity; if they 
are exposed but not actually infected the immunity is temporary. 



128 HOG CHOLEKA 

ing on serum alone plus natural infection to pro- 
tect young pigs more than four weks. 

Technique of serum administration. Require- 
ments. Serum in covered container, or in a bottle 
fitted with cannula through which it may be 
dra^vn ; hypodermic needles, and syringe, the lat- 
ter preferably one of 30 or 40 mil capacity ; anti- 
septic solution in large container, and scrub-brush, 
for disinfecting site of injection; antiseptic solu- 
tion in small container for disinfecting needles and 
syringe. In field work these are placed conven- 
iently upon an improvised table consisting usually 
of a box covered with a clean toAvel or oilcloth. 

The pig is confined in the manner already de- 
scribed, and the site of injection is thoroughly 
cleansed with the scrub-brush dampened in anti- 
septic. If syringe and needles have not been pre- 
viously sterilized, they should now be thoroughly 
disinfected, after which the required quantity of 
serum is drawn into the syringe and injected 
deeply into the tissues. As the needle is with- 
drawn it is well to pinch the skin to prevent back- 
ward flow of serum. Massage is now applied if 
required, the site of injection is again dampened 
in antiseptic, and the pig is released. 

Choice of the site of injection is governed by 
the size, condition and intended use of the animal, 
by the method of confining, and by individual 
preferences. All other things being equal we pre- 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 129 

fer the armpit because the skin covering it is 
usually clean, the serum enters the tissues freely, 
and with each step the animal takes, massage is 
automatically applied. Very young pigs are most 




Plate 20. Injecting serum behind the ear. The needle is thrust deeply 
into the loose areolar tissues, and very little force is required to 
expel its contents 

conveniently confined for injecting in the ham. 
Heavy hogs, especially pregnant sows, are almost 
always injected behind the ear, because it is safer 
and more convenient to confine them standing. 
Hogs nearly ready for market should not be in- 



130 HOG CHOLERA 

jected in the ham, and young pigs and shoats are 
not injected behind the ear. Sometimes serum 
is administered in the flank, or in the loose tissues 
immediately back of the elbow, but we believe 
neither practice has much to recommend it. 

Rapid and complete absorption of serum is 
greatly to be desired, because it gives the highest 
and most prompt immunizing effect, and tends to 
prevent abscess formation. Some will inject no 
more than 20 mils of serum in a place, believing 
that a greater quantity will be absorbed but 
slowly, but it is the placing and distribution of 
the dose, much more than its size, that govern ab- 
sorption. In real small pigs it is well to divide 
the dose, and whenever possible the practice may 
be followed in older animals. In injecting young 
pigs the parts that receive the serum should be 
kneaded gently after the needle is withdrawn; in 
larger animals the needle should be thrust deeply 
into the loose tissues immediately behind the ear, 
and after the injection is completed the ear should 
be drawn forward and vigorous massage applied 
in order to distribute the dose. Serum injected 
immediately beneath the skin, forming a distinct 
welt, absorbs but slowly, and when it fails to 
spread in the deeper tissues, as evidenced by un- 
due pressure required in making the injection, 
rapid absorption cannot be expected. A syringe 



METHODS OF USING ANTI-HOG-CHOLERA SEEUM 131 

which operates easily and requires uniform pres- 
sure on the plunger should always be selected. 

Cleaning and disinfecting the site of injection 
are processes frequently neglected, because the 
hog is proverbially difficult to infect. He can be 
infected though, as some have found to their sor- 
row. If hogs are at pasture or in clean, dry, well- 
bedded pens, cleaning is not difficult. Some sim- 
ply paint the skin with tincture of iodin, and this 
answers well when the site of injection is both 
dry and clean, but tincture of iodin is not suitable 
for use on wet surfaces. We have found nothing 
better than a good coal-tar disinfectant applied 
with a stiff scrub-brush, for this removes all dirt 
and scurf, in addition to furnishing the desired 
antiseptic action. If pigs are unusually dirty the 
site of injection should first be cleaned with warm 
soapsuds. Good technique includes thorough me- 
chanical cleansing, and nothing else will take its 
place. 

Dosage of serum. The best rule is to give at 
least as much serum as the label requires. Serum 
varies widely in immunizing units per mil, and 
although the margin of safety — the increase of 
the field dose over the laboratory test dose — ob- 
served in individual laboratories is not the same, 
doses recommended in any particular laboratory 
are, in a very general way, determined by its indi- 



132 HOG CHOLERA 

vidual methods of preparing and testing. Dosage 
is based on weight, and one not accustomed to 
estimating weights of hogs should weigh one or 
more before beginning work, for a common and 
disastrous error is to estimate far too low, and 
to give correspondingly small doses of serum. 
Not infrequently we have known weights to be 
estimated at less than half what they actually 
were. We believe a common error in dosing, and 
one for which labels are frequently responsible, 
consists of giving all hogs above a certain weight 
a fixed quantity of serum. Thus on one label we 
read: ^'Hogs 180 pounds and over, 75 mils." A 
hog weighing 180 pounds may properly receive 
75 mils of average serum, but one weighing 500 
pounds will not be adequately protected by that 
quantity. Under all conditions under which it is 
known or suspected that the hogs have resistance 
below the average, it is a wise precaution to in- 
crease the dose measurably. In badly infected 
herds it should be doubled. 

If serum is carefully administered, with due 
precautions regarding rapid absorption, it is prac- 
tically impossible to overdose, and there is no dis- 
ease or condition of swine, so far as we know, that 
even an unnecessarily large dose of serum alone 
will affect unfavorably. Thus in case of suspected 
hog cholera, in which the diagnosis cannot be 
clearly established, it may, and should be, admin- 



METHODS OF trSING ANTI-HOG-CHOLERA SERUM 133 

istered ; and in case deviation from the dose table 
seems desirable, a quantity unnecessarily large is 
preferable to one dangerously small. 

Therapeutic value of serum alone. Serum is 
employed almost entirely as a preventive of bog 
cholera, but it possesses some therapeutic value 
when used in generous doses early in the course 
of the disease. Herein lies the reason for in- 
creased doses in badly infected herds — ^many ani- 
mals apparently well are really in the first stages 
of hog cholera. Ordinarily we do not regard 
treating hogs visibly sick with cholera as a profit- 
able venture, but when the disease appears in mild 
form, or when the animals are adults or of excep- 
tional value, we are more than repaid for our 
efforts to save them. Double doses of serum are 
recommended under such circumstances, and or- 
dinary doses may follow at intervals of from three 
to seven days, as the condition of the animal re- 
quires. 

Good nursing as an adjunct to serum treatment 
is of the utmost value. A plentiful supply of fresh 
water should be furnished, to which may be added 
a saline purgative when there is constipation. 
The diet should be severely restricted, and under 
no circumstances should unconsumed food be kept 
before the animal. Warm milk alone is an excel- 
lent diet for hogs suffering with cholera. 

Dangers and after-effects of serum alone im- 



134 HOG CHOLERA 

munization. Occasionally rough handling during 
the process of vaccinating will injure an animal, 
but this is not to be charged to the effect of serum. 
Sometimes, especially in very young pigs, a tem- 
porary stiffness or lameness exists for a day or 
two following treatment, but this is exceptional, 
and usually it is of little consequence. Large 
quantities of cold serum, especially when the dose 
is not well distributed, sometimes cause this 
trouble in an aggravated form. The obvious pre- 
cautions are to use due care in injecting, and to 
warm serum that is to be administered to young 
pigs in cold weather. A temperature approaching 
blood heat is desirable, and may be secured by 
placing the bottles in warm water. 

Very exceptionally there is observed, immedi- 
ately following serum administration, a rapidly 
spreading local infection often involving an entire 
quarter and encroaching on other parts. There 
is acute lameness in the atfected quarter. The 
area involved is either doughy in consistency, or 
else gas formation is evident, and under both con- 
ditions there is pronounced edema. The skin 
usually assumes a purple hue. As a rule, animals 
thus affected die in a short time. We have seen 
but a limited number of such cases, and with one 
exception, all could be traced to gross carelessness 
in technique, or to working conditions which ren- 
dered even average technique impossible. We 



METHODS OF USING ANTI-HOG-CHOLEEA SEKUM 135 

have never seen a considerable number of animals 
in one herd thus affected. 

Abscesses follow serum administration infre- 
quently, and like the rapidly terminating type of 
infection just described, they are usually asso- 
ciated with faulty technique or conditions below 
the average as far as sanitary surroundings of 
the animals are concerned. They occur most fre- 
quently in poorly nourished, weak animals, but 
are not always thus limited, nor is it possible in 
all cases to ascribe them to bad technique. The 
bacterial flora of the particular surroundings in 
which the immunizing is done seems to play an im- 
portant part, but even this factor may be con- 
trolled to a great extent by the free use of disin- 
fectant. Dust contamination of serum and instru- 
ments also favors abscess formation, and for this 
reason one should work out of doors whenever 
possible. Failure to distribute the dose of serum 
thoroughly sometimes results in local inflamma- 
tion, leading to abscess formation. Abscesses are 
rare when the serum is not contaminated, when 
care is used in administering it, and when the 
treated animals are in reasonably clean quarters. 

Vaccination abscesses usually encapsulate and 
form slowly, and although they sometimes reach a 
considerable size and retard the growth of the 
animal to some extent, they rarely threaten its 
life or cause general symptoms of disease. If 



136 HOG CHOLERA 

they occur in the hams of hogs ready for market 
they are highly objectionable, as they cause con- 
demnation of the entire quarter in which they are 
located. The handling of vaccination abscesses 
consists of opening them when the first evidence 
of fluctuation appears, pressing out the thick, 
greenish-yellow pus which they usually contain, 
and irrigating the sac with weak antiseptic solu- 
tion. In opening, the incision should be made with 
due regard for continuous drainage. 

Considerable space has been devoted to these 
untoward results which sometimes follow serum 
administration, but on the whole they are uncom- 
mon when reasonably good technique is employed. 
One who is careful will immunize hundreds and 
even thousands of hogs mthout encountering 
difficulties of this kind, but it is well to know that 
they sometimes occur, and to understand the im- 
portance of seemingly trifling influences that 
operate to cause or prevent them. 

Summary of action of serum alone. 

1. Produces in hogs not infected with cholera 
near the time of its administration a passive im- 
munity lasting about four weeks. 

2. Produces active and permanent immunity in 
swine more than twelve weeks old that are defi- 
nitely infected mth cholera immediately before 
immunization, or during the three or four weeks 
following it. 



METHODS OF USING ANTI-HOG-CHOLEEA SERUM 137 

3. Produces an active and permanent immunity 
in many pigs less than twelve weeks old which are 
definitely infected with cholera near the time of 
treatment, but cannot be depended on to produce 
permanent immunity in all young pigs. 

4. Does not affect other diseases unfavorably, 
and if it is carefully administered, untoward re- 
sults following its use are practically negligible. 

Indications for serum alone. 

1. In seemingly well and exposed animals in in- 
fected herds. 

2. In all cases in which a four-week immunity 
will meet the requirements. (Show hogs under 
some circumstances, those near the end of the 
fattening period, breeding animals crated for 
shipping.) 

3. In all cases in which immediate protection 
is required and simultaneous treatment cannot be 
safely administered. (Sows near farrowing time, 
weak unthrifty animals temporarily threatened 
with hog cholera.) See also follow-up treatment. 

Contra-indications for serum alone. Serum 
alone is contra-indicated when the following con- 
ditions coexist in the same herd or animal. 

1. A permanent immunity is desired. 

2. Hog cholera infection does not exist. 

3. Simultaneous treatment may safely be ad- 
ministered. 

Simultaneous or double treatment. This 



138 HOG CHOLERA 

method consists of giving serum in exactly the 
same manner as has already been described, and 
of administering at the same time, and wdth a 
separate syringe, the required dose of hog cholera 
virus. Usually the dose of serum is given in one 
of the sites of injection already mentioned, and 
the virus at the corresponding point on the oppo- 
site side. The technique of administering virus 
does not differ from that employed with serum, 
except that special care is required in disinfecting 
the site of injection after the needle is removed. 
Also the dose of virus is so small that massage is 
not required. No virus should be allowed to drop 
on the ground, and all that is not used should be 
burned. 

Simultaneous treatment possesses the great ad- 
vantage of producing a permanent immunity in all 
swine that are more than twelve weeks old, and in 
many of those that are younger. On the other 
hand it involves the use of a lethal dose of hog 
cholera virus, thus producing certain sequelae and 
adding specific dangers that are not associated 
with serum alone treatment. 

Dosage of serum and virus. The same princi- 
ples that apply to dosage of serum administered 
alone, apply when it is given with virus. We give 
at least as much serum as the label indicates, in- 
creasing the dose when we are compelled to ad- 
minister simultaneous treatment to hogs below 



METHODS OF USING ANTI-HOG-CHOLEEA SERUM 139 

average in resistance. In using virus the label is 
likewise our guide. Although in giving simultane- 
ous treatment to hogs we regularly administer a 
lethal dose of virus, we should not let that fact 
tempt us to decrease the quantity. Too much 
stress has been laid on carefully graded doses of 
virus and on the necessity for balancing virus and 
serum doses. One mil of virus will kill almost as 
regularly and quickly as three, and an ordinary 
dose of serum will protect against either quantity. 
The dose of serum is not governed by the quantity 
of virus, but by the potency of the serum, which 
is reflected on the label, and by the size and con- 
dition of the hog. Thus, if circumstances compel 
us to give simultaneous treatment to hogs below 
average in resistance, we increase the dose of 
serum, but leave the virus dose unchanged. The 
primary aim is to give enough virus to infect, and 
enough serum to protect against an infecting dose. 
In our own field work we never give less than one 
mil of virus nor more than two mils, our prefer- 
ence being for a dose approaching the latter figure 
in all swine weighing more than seventy-five 
pounds. 

After-effects and dangers of simultaneous treat- 
ment. A reaction, very slight in the vast ma- 
jority of cases, but severe in others, usually 
follows simultaneous treatment. In effect, the 
animals go through an attack of hog cholera which 



140 HOG CHOLEEA 

is SO light that symptoms do not appear, but if 
temperatures are recorded the curve will usually 
show slight elevation and more or less fluctuation 
between the fifth and twelfth days following immu- 
nization. Under unfavorable conditions the reac- 
tion becomes relatively more severe, and symp- 
toms of hog cholera may appear. If these are 
slight, complete recovery will take place; if they 
are severe, they threaten the life of the animal; 
and if it dies its death is due to hog cholera just 
as truly as it would be if no serum were adminis- 
tered. Sickness and deaths due to hog cholera 
following simultaneous treatment are termed 
^'breaks'' or ^^vaccination cholera.'' If the trou- 
ble appears during the first three weeks foUomng 
treatment it is called a ^ ' serum break ' ' the suppo- 
sition being that the serum is impotent and allows 
the virus to kill the animal; if it appears after a 
longer time it is termed a ^' virus break,'' the effect 
being ascribed to the fact that inert virus has been 
administered and the serum produces only a tem- 
porary immunity, which, as it disappears, leaves 
the herd again susceptible. 

In reality, ^* serum breaks" are due to a variety 
of causes, among which are impotent serum, 
faulty technique in vaccinating, insufficient doses 
of serum, and, in addition, any influence whatso- 
ever that temporarily lowers the resistance of the 
animals during the two or three weeks subsequent 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 141 

to vaccination. Most important among these may 
be mentioned shipping, weaning, castrating, heavy 
ascaris infestation in which the gall ducts are 
tilled with the parasites, overheating incident to 
handling during immunization, severe exposure in 
cold rains during the reaction period, injudicious 
feeding during that time, and general unthrifti- 
ness due to any cause. These are not imaginary 
influences that may cause ^'breaks,'' but are real 
influences that do cause them, and while they may 
be repeatedly ignored without dire consequences, 
the tendency is to ignore them once too 
often. 

The practicing veterinarian is helpless in re- 
gard to the potency of the serum he uses. He has 
no opportunity to test it, and must therefore ac- 
cept it on faith. His safest plan is to secure it 
only from the most reliable sources. Of course if 
the virus used is up to standard, and the serum is 
impotent the hogs that receive the two simultane- 
ously will probably die, and no veterinarian who 
has had this result follow his work will soon for- 
get it. It is well to remember, though, that impo- 
tent serum is just one of many causes of so-called 
** serum breaks'' and that the remainder of these 
causes are for the most part controlled by the 
practitioner or breeder. There is a triple respon- 
sibility associated with all simultaneous treat- 
ment, and neither serum producer, -veterinarian 



142 HOG CHOLERA 

nor breeder should throw stones until he is sure 
he is not living in a glass house. 

Shipping hogs immediately after simultaneous 
treatment has been administered, or worse still, 
holding them three or four days and then shipping 
them so that they will be on the road at the time 
the reaction following treatment is in progress, is 
a fruitful cause of serum ''breaks/' We are 
aware that this practice is stoutly defended by 
many, principally by those who administer the 
treatment in stockyards, see the hogs loaded in 
cars, and never see them again. The practice is 
not defended by veterinarians who are on the re- 
ceiving end of the line, for it is a well-known fact 
that ' ' serum breaks ' ' often occur soon after these 
hogs reach the farms on which they are to be 
fattened, and it is fortunate indeed if hog cholera 
is not thus transmitted to other herds in the vi- 
cinity. This method of handling hogs may be 
necessary under present conditions, even if it must 
carry with it the risks we have mentioned, but 
granting that it is necessary, let us at least recog- 
nize the dangers in their true proportions, and 
work toward a better method of handling feeding 
hogs. 

Lowered resistance due to shipping accounts 
for many of these ''breaks,'' yet the tendency is 
to charge them to impotent serum. The best se- 
rum that can be manufactured will not protect all 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 143 

animals thus handled, but the fact that many lots 
of hogs will endure it, leads some to think that all 
ought to do so. Individual differences exist, and 
while they are not always obvious, the lots that 
** break '^ more often consist of hogs that have 
been held in stockj^ards a long time, those badly 
infested with parasites, or suffering with respira- 
tory diseases. Distances traveled to and from the 
stockyards, and the degree of crowding of the cars 
are also potent factors in determining the hazards 
of shipping simultaneously treated hogs. 

Hogs are not fit subjects for simultaneous treat- 
ment just as they are unloaded from long railway 
journeys. It is best to give these animals serum 
alone at this time, and simultaneous treatment 
two or three weeks later. This is the follow-up 
treatment w^hich we have already mentioned, 
and which will be considered separately in this 
chapter. 

In farm hogs, weaning, castrating, ringing, and 
the absurd practice of knocking '^ black teeth '^ out 
of all pigs may operate individually or collec- 
tively to lower resistance and render simultaneous 
treatment dangerous. Due to pressure of other 
work pigs are frequently neglected several weeks, 
then suddenly there is a desire to do all of these 
things, and immunize, at the same time, in order 
to avoid handling the animals more than once. 
The wonder is that pigs will frequently, even usu- 



144 HOG CHOLEEA 

ally, survive the ordeal, but exceptions prove the 
rule — and embarrass the veterinarian. In several 
instances we have known men to castrate pigs dur- 
ing the week following simultaneous treatment. 
In some of these a number of the castrated pigs 
died, while the female pigs, which remained as 
checks, survived, thus furnishing excellent but 
rather involuntary and costly experiments. Pigs 
are best castrated as sucklings, but in any event, 
it is well to separate castrating and simultaneous 
treatment at least two or three weeks. 

Ascarids may exist in the intestine in large 
numbers without appreciably lowering the resist- 
ance of simultaneously treated pigs, but if the 
parasites enter and occlude the gall duct, the in- 
fested hog shows a remarkable intolerance for 
virus. We have observed this intolerance again 
and again both in test pigs and in the field. Prac- 
titioners cannot always avoid trouble due to as- 
carids, for granting that they know the parasites 
exist in a herd, it is not always possible to deter- 
mine their location in the individual, and often 
it is not safe to delay treatment. Severe jaundice 
in pigs is usually due to ascarids in the gall-duct, 
and its presence, easily observed in white pigs, 
should suggest caution. 

Overfeeding is injurious to pigs passing through 
the reaction following simultaneous treatment. 
Any one who has observed serum tests knows 



m:ethods of using anti-hog-cholera serum 145 

that. Often there is no change in the appetite 
during this time, but if a few animals in a lot eat 
scantily, the others gorge themselves on the sur- 
plus thus rendered available, and a period of dis- 
tress or dullness follows, during which the virus 
may get in its work. A simple rule is to feed so 
that the animals remain just a little hungry after 
each meal, and to be prepared for a slight lagging 
in appetite between the fifth and twelfth days fol- 
lowing treatment. 

Methods of preventing ^* serum breaks'' are ob- 
vious when the causes of these ^^ breaks" are un- 
derstood. Full doses of potent serum adminis- 
tered with due regard for rapid absorption, and 
proper caution in regard to treating hogs below 
average in resistance are the two essential con- 
siderations. 

Handling *^ serum breaks" involves first of all 
informing the owner of the animals, before serum 
is administered, that such ^^ breaks" are possible 
but by no means probable, and asking him to ob- 
serve the herd carefully and report any sickness 
that may appear during the three weeks following 
treatment. Should a ^' break" occur prompt 
measures are required. If only two or three hogs 
out of a herd of considerable size appear dull, and 
if these have sickened later than the twelfth or 
fourteenth day following vaccination, it is well to 
take temperatures on several animals in the herd. 



146 HOG CHOLEKA 

If the temperatures vary between normal and a 
little above 104° F. and if there is no visible dull- 
ness, serum alone may be given to the sick ani- 
mals only; but if sickness appears before the 
tenth day, if several hogs are dull, or if a number 
of them show temperatures near 106° F. the entire 
herd should receive full doses of serum alone 
without delay. Most * ^breaks," taken in time, can 
be checked. 

Abortion in sows has been caused by simultane- 
ous treatment, but it is rather unusual, and occurs 
most frequently during ^^ breaks'' due to the 
causes we have mentioned. Sows near farrowing 
time certainly should not receive serum and virus, 
but when they are in the early period of gestation 
we are frequently compelled to assume the slight 
risks as a necessary evil. 

Stunting may result from simultaneous treat- 
ment, and we are told that one of America's most 
famous pure-bred breeders had his herd ruined by 
unthriftiness following vaccination. We do not 
know the particulars, but we do know that such 
consequences need not follow simultaneous treat- 
ment judiciously administered, and we know that 
hundreds of pure-bred breeders maintain fine 
herds immune, and are satisfied. We have al- 
ready enumerated a few of the factors which cause 
* ^breaks." Any one of these may cause death, or 
falling just short of such a result, stunt the ani- 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 147 

mal. Thus it is the abuse of simultaneous treat- 
ment rather than its use which incriminates it. 

Elimination of hog cholera virus in the excre- 
tions of simultaneously treated pigs sometimes 
takes place for a few days during the resulting 
reaction. There was a time when this fact was 
denied, but no person experienced in handling hog 
cholera would seriously question it to-day. Reac- 
tions vary between one extreme in which no tem- 
perature elevation is recorded, and the other 
rather unusual one in which death takes place. In 
the first instance virus elimination is rare, but as 
the latter extreme is approached, it is the rule. 
Most hogs do not eliminate infectious material, 
but the exceptions to the rule are so numerous that 
it is not safe to keep susceptible animals with 
those that receive simultaneous treatment. 

Because of the danger of virus elimination, a 
period of quarantine is usually imposed on simul- 
taneously treated hogs. The duration of this 
quarantine is prescribed by law in most states, the 
usual time varying between twenty-one and thirty 
days, with extension in case ^^vaccination chol- 
era^' appears. Hogs that have shown no physical 
evidence of disease are very rarely eliminating 
•virus at the end of twenty-one days following 
serum-virQs immunization. 

''Virus breaks" are not manifest until several 
weeks following simultaneous treatment, and they 



148 HOG CHOLEEA 

are due to inert virus, insufficient doses, and, very 
probably, to giving simultaneous treatment to 
pigs too young. If virus is inert infection is not 
produced, active imniunity is not established, and 
if hogs chance to be exposed to cholera after the 
passive immunity due to the serum has disap- 
peared, they readily contract the disease. If a 
pig more than twelve weeks old receives a full 
dose of virulent virus as a part of simultaneous 
treatment and remains well during the following 
four weeks, his immunity to cholera may be ac- 
cepted as a fact ; if a herd that is given simultane- 
ous treatment passes the first four weeks without 
incident and later *' breaks" with hog cholera, we 
may safely assume that inert virus was used, or 
that doses ridiculously low were administered. 
Sometimes inert virus is sent out with impotent 
serum that will protect against no other kind; 
sometimes virus is used too long after being 
drawn; and if it is heated — we do not believe it 
should be — there is some danger of killing it. 

Prevention of ^' virus breaks," when one under- 
stands their causes, is simple. Provided one 
treats pigs more than twelve weeks old, a full dose 
of virulent virus in conjunction with the serum 
used in simultaneous treatment is all that is re- . 
quired. A breeder who is familiar with the bene- 
fits and hazards of simultaneous treatment will 
not be greatly disturbed if a shoat or two should 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 149 

die of ^^vaccination cholera'^ when he has his herd 
immunized; he may even view a more serious 
^' serum break'' complacently, but if his swine re- 
ceive simultaneous treatment as shoats and die of 
hog cholera when they are about ready for market, 
he has a real grievance, which he will be slow to 
forget. It is fully as important that virus shall be 
virulent as it is that serum shall be potent. 

** Hemorrhagic septicemia" forms a convenient 
and altogether too common alibi for both * ^ serum 
breaks" and ^ Virus breaks." If either occurs 
(and disease which is really hog cholera is called 
*' hemorrhagic septicemia"), this automatically 
absolves from all blame the serum producer who 
sells impotent serum or inert virus ; it excuses the 
man who abuses the products in administering 
them, as well as the breeder who subjects his ani- 
mals to improper care during the resulting reac- 
tion. The only defect in such an alibi is that it 
does not save the hogs or tell us what really kills 
them. When hogs kept under average farm con- 
ditions receive simultaneous treatment and any 
considerable number of them develop febrile dis- 
ease during the following three weeks, unless a 
cause other than ^^hemorrhagic septicemia" is 
obvious the chances are ten to one that the primary 
cause of the disease is hog cholera virus. Under 
such conditions no other cause can be accepted 
unless negative filtration experiments, requiring 



150 HOG CHOLERA 

about ten days, are carried out. The field man 
who represents a laboratory which sells question- 
able serum, and who pronounces such ''breaks'^ 
*^ hemorrhagic septicemia'' on information ob- 
tained from a few autopsies or a brief bacterio- 
logical examination, must, in mercy, be called 
ignorant, or else his honesty must be questioned. 
Most ^'breaks" can be prevented, but some cannot. 
Let us prevent those we can, and call the others 
hog cholera. That is what they are. 

Under conditions existing in the United States 
during the last decade simultaneous treatment has 
been a great boon to the swine industry; it has 
saved hogs worth millions of dollars ; it has made 
it possible for any breeder who will, to banish fear 
that hog cholera will destroy his herd. But in 
spite of these facts it is not perfect in its opera- 
tion; it is sometimes instrumental in spreading 
the disease it is intended to check ; it involves some 
dangers. These are best avoided when their 
causes are fully understood ; best combated when 
they are frankly admitted to exist. 

Forewarned is forearmed. Any veterinarian 
who contemplates using simultaneous treatment 
in a client's herd should tell him that it involves 
a little danger; that the herd must be carefully 
handled for about three weeks; that if a ''break" 
should occur it must be reported promptly, and 
that under no circumstances are susceptible hogs 



METHODS OF USING ANTI-HOG-CHOLEKA SERUM 151 

to come in contact with vaccinated ones during 
the four weeks following treatment. It is some- 
times difficult to mention these things, without 
causing the dangers to be exaggerated in a client's 
mind, and some breeders will decide not to take 
risks which they would readily assume could they 
know how slight they really are. Nevertheless a 
veterinarian's first duty is to protect his client, 
and he must protect himself if he is to remain in 
practice. The man who glibly advises that there 
is **no danger'' following his vaccinating is not 
doing either. 
Summary of action of simultaneous treatment. 

1. Produces an active permanent immunity in 
all hogs more than twelve weeks of age. 

2. Produces active immunity in some suckling 
pigs, passive immunity in others. 

3. Usually produces a very mild reaction begin- 
ning about five days following treatment, and last- 
ing less than seven days. 

4. In hogs with low resistance,^ sometimes pro- 
duces a severe reaction which exceptionally ter- 
minates in death. 

5. Causes some hogs to eliminate hog cholera 
virus in their excretions during the time the reac- 
tion is in progress. 

^ The terms ' ' resistance ' ' and ' ' condition ' ' should not be con- 
fused. The former, as used here, applies to the state of the ani- 
mal's natural defenses against disease, and is determined by the 
history, as well as by the appearance of the animal. "Condition" 



152 HOG CHOLEKA 

6. May cause abortion in pregnant sows, and 
may stunt pigs if they are treated while their re- 
sistance is low. 

Simultaneous treatment is indicated in herds 
where hog cholera virus is almost sure to find its 
way sooner or later, but where actual infection of 
the herd may be delayed several weeks or months. 
Such conditions exist : 

1. In sound herds on infected farms. 

2. In other herds immediately threatened with 
cholera. 

3. In some show hogs. See ^4iandling show 
hogs'^ in Chapter IX. 

4. On farms on which hog cholera has appeared 
periodically. 

5. In very large herds in which there is con- 
stant exchange of animals. 

6. In garbage-fed herds. 

Simultaneous treatment is contra-indicated: 

1. When it cannot be applied by experienced 
men. 

2. When the entire herd cannot be immunized. 
(Some may, if necessary, receive serum alone, but 
none must be left susceptible.) 

applies more specifically to the degree and quality of flesh an 
animal carries, as well as to the appearance of the coat, and is 
determined, in hogs, principally by inspection. Fat hogs recently 
shijjped or fat sows that have recently farrowed, though in good 
condition, will not tolerate simultaneous treatment nearly as well 
as ordinary farm hogs in very moderate flesh. The "resistance" 
of the latter is higher, although their "condition" is lower. 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 153 

3. When the treated herd cannot be properly- 
segregated. 

4. For sucking pigs as a routine measure. (In- 
formation still incomplete on this point.) 

5. For sows about to farrow, or for those nurs- 
ing young litters. 

6. In badly infected herds. 

7. In animals with low resistance due to ship- 
ping, weaning, castrating and other influences. 

8. In all circumstances in which serum alone 
will be equally etfective. 

FoUow-up treatment. This consists of giving 
serum alone and following it in a few weeks, usu- 
ally less than four, with simultaneous treatment. 
It has been called ^^ double treatment'' by some, 
but according to usage which has now become 
fixed, the terms ^^ double treatment'' and ** simul- 
taneous treatment" are applied interchangeably 
to serum-virus administration. It therefore seems 
desirable to apply to serum alone followed by 
simultaneous treatment, the separate, distinct and 
self-explanatory term, * ^follow-up treatment." 

Follow-up vaccination is safer than simultane- 
ous treatment, it can be applied under circum- 
stances which practically forbid the use of the 
latter method, and the final result is the same — 
a permanent immunity is established. There are 
those who believe that the passive immunity pro- 
duced by the dose of serum alone prevents the re- 



154 HOG CHOLERA 

action and consequent permanent immunity due 
to subsequent serum-virus treatment. The im- 
pression seems to prevail that there is just one 
way to immunize a hog permanently, and that is 
to give him simultaneous treatment as a first and 
only measure. Various troubles following follow- 
up treatment have been cited as proof of this 
theory, but we have never investigated a case in 
which there was the least evidence that the system 
was fundamentally at fault. The trouble has been 
in its application. 

In applying the follow-up system, there is a 
marked tendency for the veterinarian to give the 
dose of serum alone and to neglect for too long a 
time to follow it ^viih. simultaneous treatment. 
There is no danger in this unless the pigs happen 
to be exposed to cholera after the passive immu- 
nity due to the dose of serum has disappeared, 
but too often just that very thing takes place. The 
owner of the animals derives a false sense of se- 
curity from the fact that serum has been adminis- 
tered, and hence does not report the sickness as 
promptly as he otherwise would. The final result 
is that when hog cholera is well started in the 
herd, the veterinarian receives an urgent call to 
give serum and virus as the final installment of 
the follow-up treatment. Heavy losses inevitably 
follow, and the entire system is condemned. It 
should always be remembered that serum alone 



METHODS OF USING ANTI-HOG-CHOLEKA SEKUM 155 

cannot be depended on to protect more than four 
weeks. 

*^ Virus breaks^* are no more likely to occur 
when follow-up treatment is administered than 
they are following simultaneous treatment, and, 
as with the latter method, their prevention con- 
sists wholly of giving full doses of virulent virus, 
and using due care not to treat pigs too young. 
When these precautions are observed, we can 
vouch for the fact that follow-up treatment pro- 
duces a permanent immunity. We have used it 
since 1912 in maintaining many immune herds, 
usually administering the final dose, simultaneous 
treatment, when the pigs were about twelve weeks 
old. We have not had a ^* virus break ^' during 
the nine years the system has been employed; 
that is, no pigs that survived the immediate reac- 
tion following the final serum-virus treatment sub- 
sequently developed hog cholera. It is our custom 
to select hypers from these herds, and so far none 
of them have developed hog cholera as a result 
of hyperimmunization. In the East many veteri- 
narians use the follow-up system in maintaining 
herds immune to cholera, and ** virus breaks'' are 
not common. 

Experimentally we have tested the effects of 
giving follow-up t;:eatment using various inter- 
vals between the time of administering serum 
alone and that of administering serum and virus. 



156 HOG CHOLERA 

and trying to smother the action of virus by large 
and repeated doses of serum alone previous to 
simultaneous treatment. In no case have we ob- 
tained evidence to justify even a suspicion that 
follow-up treatment does not produce permanent 
immunity, and we know of no experimental work 
that contradicts these results. 

The factor of greater safety cannot well be 
questioned, although it is seldom that hogs with 
average resistance require follow-up treatment. 
Simultaneous immunization produces the same re- 
sult, and is cheaper. But if exceedingly valuable 
animals are to be immunized, one cannot go amiss 
in giving a dose of serum alone and following it 
in a week or two with simultaneous treatment. If 
the first dose of §erum is in the system, already 
absorbed, when the second dose is given with 
virus, there can be no question that the hazards 
are reduced. Exact comparisons of the safety of 
simultaneous and follow-up treatment are difficult 
to make, because under ordinary conditions both 
are nearly 100 per cent effective. We have seen 
follow-up treatment used in immunizing cattle 
against rinderpest \vith losses running less than 
5 per cent when simultaneous treatment with the 
same serum and virus caused such heavy losses as 
to forbid its use altogether. "We do not care to 
generalize too far on this point, but the princi- 
ples employed in preparing and using the two se- 



METHODS OF USING ANTI-HOG-CHOLERA SERUM 157 

rums are the same, and we offer the observation 
for what it is worth. 

Follow-up treatment is indicated: 

1. For very valuable hogs where the greatest 
possible safety is required. 

2. "When the following conditions coexist in the 
same animal or herd : 

A. Immediate protection is imperative. 

B. Ultimate permanent immunity is desired. 

C. Conditions render immediate simultaneous 
treatment dangerous. 

Follow-up treatment is contra-indicated in all 
cases in which it appears 'that serum alone or si- 
multaneous treatment will be equally eif ective. 

It is in immunizing hogs mth resistance obvi- 
ously below normal, and in maintaining immune 
herds under somewhat adverse conditions that 
follow-up treatment renders greatest service. In 
practice, especially in the East, we constantly en- 
counter the three conditions we have enumerated 
above, and follow-up immunization relieves us 
from the necessity of choosing between serum 
alone which will not produce a permanent immu- 
nity, and simultaneous treatment which is posi- 
tively dangerous at the time when immediate pro- 
tection is required. In a succeeding chapter the 
adaptations of follow-up treatment will receive 
further attention in connection with specific con- 
ditions which we meet in the field. 



CHAPTER IX 

HANDLING HOG CHOLEKA IN THE FIELD 

Handling hog cholera in the field requires ap- 
plication of the principles that have been outlined 
in preceding chapters. In this chapter our plan 
is to assume the existence of certain actual con- 
ditions which the practitioner frequently meets 
in the field, and to suggest methods of hiandling 
suited to these conditions. We know that in doing 
this we may invite criticism, for methods of han- 
dling hogs are so mdely different in various parts 
of the country that one cannot supply details that 
will apply everywhere. 

In some parts of the South, for instance, where 
hogs are allowed almost unlimited range, where 
predatory animals are common, where hog cholera 
is prevalent, and where a few breeders use simul- 
taneous treatment regularly, others must protect 
their hogs in the same manner, or lose them. In 
certain sections of the corn-belt hog cholera is 
prevalent to such a degree that it is the part of 
wisdom for practically all breeders to maintain 
immune herds. In the East, where hogs are rather 
closely confined, w^here they are raised in limited 

158 



HANDLING HOG CHOLERA IN THE FIELD 159 

numbers, where hog cholera is not common and 
its spread is not rapid, most herds do not require 
immunization. Moreover, in the corn-belt where 
hog raising is a business, methods of swine hus- 
bandry are relatively much better than they are 
in sections in which it is a mere adjunct to 
other farming operations. The average corn-belt 
breeder has had more or less experience with hog 
cholera, he knows what it means to have it sweep 
unchecked through his herd, and he is not in- 
clined to be dissatisfied with measures that will 
check it, even though these measures may not 
always be perfect in their operation. On the other 
hand, the Eastern breeder whose herd we are 
called on to handle very often is having his first 
experience with the disease, he is inclined to be 
skeptical as to the merits of protective serum, and 
to doubt its value if he loses a few animals after it 
has been administered. Frequently also, the herd 
is found in unthrifty condition due to poor meth- 
ods of swine husbandry and heavy parasitic in- 
festation. Virus cannot be used as freely in such 
surroundings as it can under circumstances where 
its effects will be more correctly judged. 

Despite these differences, though, and despite 
the fact that methods of swine husbandry have a 
direct and important bearing on the handling of 
disease, the principle holds that hog cholera is 
hog cholera the country over, and not, as some 



160 HOG CHOLERA 

would have us believe, different according to the 
section of the country in which we chance to find 
it. The differences we observe in various parts of 
the country are due principally to prevailing sec- 
ondary invaders, as well as to variation in viru- 
lence of the hog cholera virus itself, for they are 
observed also in comparing individual herds or 
outbreaks in any one section. 

While we must accept all these variations and 
allow for them, the underlying principles em- 
ployed in handling hog cholera remain unchanged, 
and it is desirable and necessary in a treatise of 
this kind to suggest definite working plans, leaving 
the reader to alter or supply detail as individual 
cases warrant. We are moved to do this because 
we have seen young graduates of veterinary col- 
leges who had had good instruction and whose 
technique in administering serum left little to be 
desired — we have seen some of these men practi- 
cally helpless in the presence of outbreaks of 
cholera which presented disturbing but not un- 
usual features. Likewise men who are accus- 
tomed to the routine of vaccinating thousands of 
stockyard hogs are sometimes confused when they 
are called on to accept the conditions they meet 
on the average farm, to prescribe treatment for 
a mixed lot of swine, and guide the breeder away 
from future trouble. Mere knowledge of how to 
vaccinate hogs does not equip one to handle hog 



HANDLING HOG CHOLEKA IN THE FIELD 161 

cholera; diagnosis, when and whether to vacci- 
nate, the method to use, and the subsequent han- 
dling of the herd all enter into the problem. 

Handling the cholera infected herd. Let us 
assume, as a working basis, that a herd consisting 
originally of one hundred ordinary shoats, in good 
condition, is infected with hog cholera; ten have 
died, ten are visibly sick, and there is no evidence 
of secondary infection; there are no other hogs 
on the farm, and the shoats are in a pasture con- 
taining several acres; the owner has had hog 
cholera in his herd in previous years, and knows 
the results that may reasonably be expected from 
preventive measures. This represents the sim- 
plest situation we are called on to cope with in 
handling hog cholera in the field. 

Three methods of handling are open to us : 

1. Give generous doses of serum alone to all 
animals that are not exceedingly weak. 

2. Give simultaneous treatment to all seemingly 
well animals, and double doses of serum alone to 
those that are visibly sick, and not obviously near 
death. 

3. Give serum alone in full doses to all ani- 
mals that are apparently well, in double doses to 
those that are sick and have a chance to recover, 
and follow this in three weeks with simultaneous 
treatment for all animals that were not visibly 
sick at the time of the first treatment. In other 



162 HOG CHOLERA 

words, give serum alone to the sick animals, fol- 
low-up treatment to those that are apparently 
well. 

Eegardless of the method selected, we must 
proceed promptly with the one that becomes our 
final choice, and we must take immediate precau- 
tions to prevent spread of the disease to other 
herds. 

Method mimher one may prove highly satisfac- 
tory in some cases of this kind, but it is open to 
the serious objection that it may not produce per- 
manent immunity in all the animals. In the indi- 
vidual, serum alone plus hog cholera infection 
produces permanent immunity, but in a herd of 
this kind, although all the animals are exposed, 
some may not become infected in time to secure 
this result, because hog cholera does not always 
spread rapidly through herds that are at pasture 
or in other large runs. 

Let us select, as an instance, one shoat in the 
herd and assume that the animal has received 
serum alone to-day. If in the course of the next 
three or four weeks — the usual duration of immu- 
nity due to serum alone — it chances to take up 
virus sufficient to infect, it will undergo a reaction 
and thereafter be permanently immune to hog 
cholera; but if the event of infection is delayed 
much longer, it will find the animal susceptible to 
the disease. In other words, if infection takes 



HANDLING HOG CHOLERA IN THE FIELD 163 

place while passive immunity due to serum alone 
still exists, a permanent immunity is acquired; 
if it takes place after the passive immunity dis- 
appears, the animal will readily contract hog 
cholera; and, except where hogs are quite closely 
confined, chance alone must decide whether any 
particular individual will become permanently im- 
mune, or, failing in this, eventually die of hog 
cholera. 

Method number two will produce more reliable 
results. The sick are distinguished from the well 
by physical appearance and temperature read- 
ings. In handling herds in this manner it is our 
custom to give serum alone to all animals showing 
temperatures above 104° F., and to all visibly sick, 
and not at the point of death, regardless of tem- 
perature reading. If, however, the weather is 
warm, and if the hogs are excited in handling, 
most temperatures will rise above this point, and 
the thermometer gives us very little information. 
Under such circumstances physical appearance is 
our only guide. A useful practice, whenever con- 
ditions are such that it can be employed, is to feed 
the hogs a little grain and to place those that leave 
the feed in a few moments among the sick that are 
to receive serum alone, and those that remain for 
a longer time and eat greedily, among the well 
that are to receive serum and virus. Practically 
all will eat a little, but the infected animals are 



164 HOG CHOLERA 

first to leave their feed. Any method of distin- 
guishing tlie sick from the well is only approxi- 
mately correct, but a herd handled in the manner 
we have outlined mil emerge from the treatment 
permanently immune to hog cholera. On the 
whole, this method of handling is quite satisfac- 
tory, but it is open to the objection that we may 
introduce a more virulent strain of virus into 
herds already infected, and we may be. accused of 
killing animals when we have merely failed to pre- 
vent their death. 

This method is practicable only when the owner 
of the animals fully realizes that some apparently 
well hogs in infected herds will die following even 
serum alone administration, and when he is dis- 
posed to expect like losses following serum-virus 
treatment. Veterinarians experienced in handling 
hog cholera dread to use virus in infected herds, 
but we meet conditions under which it is wise to 
do so. 

Method number three is safest, and, as with 
method number two, the herd emerges with all 
animals permanently immune to hog cholera. The 
added expense is the only objection, but in many 
instances, especially when the animals are above 
average in value, it is more than justified. There 
is great satisfaction to the practitioner, as well as 
to the breeder, in knowing that nothing has been 



f 

HANDLING HOG CHOLERA IN THE FIELD 165 

done to add fuel to the flames, and in being al- 
lowed tliree weeks ' respite in which to observe the 
progress of an outbreak. 

Irrespective of the plan we choose, if new cases 
continue to appear later than the sixth or seventh 
day following treatment, a second dose of serum 
alone is indicated; and if ^^ breaks'' occur subse- 
quent to simultaneous treatment, they should be 
handled in the manner described in the preceding 
chapter. 

Under the conditions in which we found this 
herd of shoats, we explain the situation to the 
breeder, and recommend method number three as 
safest, informing him at the same time that 
method number two is, in the majority of cases, 
satisfactory. With the facts before him he can 
then decide for himself. 

Precautions to prevent spread of hog cholera to 
neighboring farms include preventing sale or ex- 
change of sick or well animals from the infected 
herd, exclusion from the infected pasture of all 
persons, vehicles, or animals that may later enter 
non-infected hog quarters, and prompt disposal 
of carcasses so that they will not attract carrion- 
eating animals or birds. Burning is by far the 
best method of destroying carcasses, but burying 
in quicklime, or rendering, is permissible. In a 
pasture such as we find this herd of shoats dis- 



166 HOG CHOLERA 

infectants are of little service, and we must de- 
pend on natural influences (drying and sunlight) 
to destroy virus which contaminates the soil. 

Many states have specific regulations governing 
precautions against interherd spread of hog chol- 
era, and when these are available and practicable 
they should be followed. None of the shoats 
should be removed earlier than thirty days follow- 
ing disappearance of all sickness from the herd, 
and previous to their removal, if they are to min- 
gle with cholera susceptible hogs they should first 
be dipped or sprayed with 3 per cent compound 
cresol solution. It is legal in some states, in han- 
dling a herd of this kind, to remove apparently 
well animals for immediate slaughter under in- 
spection, but except in unusual circumstances the 
practice has little to recommend it. 

If we go back to our original problem and as- 
sume alterations in the conditions there outlined, 
corresponding changes in the plan of handling will 
suggest themselves, and the reasons for these 
changes will appear. If hogs are closely confined 
and the herd is badly infected, serum alone is indi- 
cated, because natural infection will take place 
and produce permanent immunity in all that sur- 
vive ; if they are found under conditions that sug- 
gest low resistance, if they are of exceptional 
value, or if the owner is skeptical, nervous, or 
overcritical, plan number three should be recom- 



HANDLING HOG CHOLEEA IN THE FIELD 167 

mended, special care being taken to build up the 
resistance of the animals during the interval be- 
tween serum alone and serum-virus administra- 
tion. 

If, as is sometimes the case, we are compelled to 
make a provisional diagnosis of "hog cholera, we 
should give serum alone and observe the future 
development of the disease. Provided it proves to 
be hog cholera, or if it disappears entirely so that 
doubt still remains, we may give simultaneous 
treatment three or four weeks later; if it proves 
to be some other malady, and if hog cholera is not 
in the vicinity, simultaneous treatment should not 
follow unless the OAvner wishes to maintain an im- 
mune herd. Usually, when there is hog cholera 
together with some active complication, the im- 
munity of the herd should be maintained on serum 
alone until the animals are in fit condition to re- 
ceive serum-virus treatment. This may require 
two or more doses of serum at three or four week 
intervals, but if the complication is of such nature 
that it cannot be controlled after serum alone is 
administered, we mil only aggravate it if we give 
simultaneous treatment. 

Methods of preventing spread of hog cholera to 
neighboring herds are also somewhat different 
when we find the infected animals closely confined. 
We gain very little by cleaning and disinfecting 
quarters occupied by hogs sick with cholera, be- 



168 HOG CHOLERA 

cause each time an infected animal urinates, rein- 
fection of its pen takes place. As long as hog 
cholera is active in a herd we should devote our 
attention to elTective quarantine, prompt disposal 
of carcasses, and the maintenance of ordinary 
cleanliness that is at all times conducive to the 
health of the animals. When the disease disap- 
pears, all contaminated litter should be burned, 
and the indoor quarters sprayed vdth. 3 per cent 
lysol or compound cresol solution. Often appli- 
cation of disinfectant at intervals of several days 
is advantageous. Hog cholera virus cannot al- 
ways be killed in outside yards. Spreading a 
thick layer of straw over the yard and burning it 
is probably most effective, but this is not always 
practicable. Plowing and free use of disinfec- 
tants hasten destruction of the virus, but the lat- 
ter measure is useful only in small enclosures. 

Too often directions given for disinfecting quar- 
ters require more than is possible, and they are not 
specific. If we are careful not to require unneces- 
sary and laborious measures we will secure much 
better cooperation in carrying out those that actu- 
ally are essential; and if surroundings are such 
that we find it impossible to give detailed and spe- 
cific directions for cleaning and disinfecting, we 
may be sure that the general admonition to ' * clean 
and disinfect'' will do very little good. We must 
recognize the fact that some hog quarters cannot 



HANDLING HOG CHOLERA IN THE FIELD 169 

at once be freed of hog cholera virus, at least by 
methods within reach of the man of average 
means. Under such circumstances, if hog raising 
is to be continued, the herd should be maintained 
immune to hog cholera. 

We have already said that handling a herd of 
infected shoats is the veterinarian's simplest duty 
in dealing with hog cholera. We will now con- 
sider some of the more complex problems that field 
work constantly place before us. Let us suppose 
that in addition to the herd of infected shoats 
there is on the same farm, some distance away, a 
number of feeding hogs that have shown no signs 
of disease. If the animals are to be marketed 
in less than four weeks they may receive serum 
alone, and if hog cholera does not appear among 
them in the course of six or seven days, it is allow- 
able to kill them under inspection; if marketing 
must be delayed more than four weeks, simultane- 
ous treatment is indicated. As far as the effect 
of treatment itself is concerned, hogs may, if 
emergency demands it, be killed for food as early 
as one day following administration of serum 
alone, but if serum and virus are given, a delay of 
at least three weeks is desirable. 

In addition to feeders we encounter on practic- 
ally every farm a considerable number of breeding 
stock. A boar, pregnant sows, some just farrow- 
ing, and others nursing litters make up the repre- 



170 HOG CHOLEKA 

sentative farm herd. A permanent immmiity is 
desired for all of these, and we follow the general 
plan of giving simultaneous treatment to all ani- 
mals in condition to receive it, and protecting the 
others with serum alone pending the time when 
they may safely receive serum and virus. 

Assuming that breeding stock of this character 
is on the farm with the infected shoats, but that 
after numerous temperatures have been taken 
there is no evidence of disease, it may be handled 
as follows : the boar may be given serum and virus 
at once, or if he is of exceptional value, follow-up 
treatment; sows in early pregnancy may be han- 
dled in the same manner, but always after the 
breeder has been informed that simultaneous 
treatment will sometimes produce abortion, and 
that the slight danger must be accepted as a lesser 
evil ; sows due to farrow in less than three weeks 
and those that have pigs a few hours or days old 
cannot safely receive virus. It is true that the 
infection on the farm will in most cases ultimately 
reach them, but our aim should be to delay this as 
long as possible, and to protect the sows with 
serum alone in the meantime. Continued isola- 
tion of the sows is desirable. Two or even three 
doses of serum alone at three or four- week inter- 
vals may be required before the time is ripe for 
the final simultaneous treatment, but the extra ex- 
pense is greatly to be preferred to the alternative 



HANDLING HOG CHOLEEA IN THE FIELD 171 

— that of using simultaneous treatment so that the 
sow will be farrowing or nursing a newborn lit- 
ter at a time when the resulting reaction is in 
progress. 

The pigs likewise should be maintained on doses 
of serum alone at four-week intervals until they 
are at least nine w^eeks old, preferably twelve, and 
then they should receive simultaneous treatment. 
If they are fairly well isolated from the infected 
animals the first dose of serum alone may be de- 
layed until they are two or three weeks of age, 
otherwise it should be given when they are only 
a few days old.^ 

^ The question whether young pigs acquire a permanent immu- 
nity as a result of simultaneous treatment is yet unanswered. 
Niles describes experiments indicating that they do, while Cahill 
on the other hand found that over 50 per cent of several hundred 
pigs given serum and virus betAveen the ages of two and eight 
weeks failed to acquire a permanent immunity as a result. Peter- 
sen found that only fifteen out of one thousand ' ' baby pigs ' ' 
given simultaneous treatment proved susceptible as old hogs. We 
have collected very little experimental data on this point, the 
results agreeing substantially with those of Niles. 

Our field observations, however, lead us to believe that a per- 
manent immunity is not always established Avhen serum and virus 
are given to sucking pigs. In one instance we gave simultaneous 
treatment to fifty pigs that were about eight Aveeks old. When 
the animals had reached a weight of about 150 pounds, one of 
them was brought to us for autopsy and showed undoubted lesions 
of hog cholera. Three or four of the others developed symptoms 
of the disease during the following week, so the entire herd was 
revaccinated. Two of those that sickened died later but we did 
not have an opportunity to perform autopsies. There is little 
doubt that they died of hog cholera, but just how many more 
would have died in the absence of a second injection is a matter 
of conjecture. In another instance that came under our observa- 
tion about eighty young pigs were given simultaneous treatment, 
and when these animals reached a weight of about 180 pounds 
each, approximately twenty of them died. We performed autop- 
sies on several, and found unmistakable hog cholera lesions. 



*1! 

172 HOG CHOLERA f i 

We have been called on repeatedly to handle 
herds of sows infected mth hog cholera just at 
farroAving time. Whenever it is possible we dip 
the animals, segregate them as best we can and 
administer serum alone, carrying both sows and 
pigs along mth doses of serum alone at four- 
week intervals until the latter are weaned and at 
least nine weeks old, at which time sows and pigs 
receive simultaneous treatment. In herds in 
which isolation is impossible, we follow the same 
course in regard to administering serum, giving 
the first dose, about 4 mils, when the pigs are a 
day or two old. It is possible to bring pigs safely 

These observations do not carry the weight that may be attached 
to carefully controlled experiments, but they suggest caution in 
regard to the sweeping conclusion that all young pigs acquire 
permanent immunity as a result of simultaneous treatment. 

Closely bound up with this question is the one of the immunity 
of sucking pigs to hog cholera. Pickens found that 100 per cent 
of pigs nursed by immune mothers Avere themselves immune, but 
any person with extensive experience in handling hog cholera 
knows that we cannot always, or usually, depend on this immunity. 
We have repeatedly seen pigs born of immune mothers and 
nursed by them dead with hog cholera before they were four 
weeks old, but there are others, as Pickens' experiments show, 
that are immune. 

Collectively, all experimental work and clinical observations so 
far recorded point to the conclusion that some pigs of cholera 
immune mothers are themselves immune, and others are not; some 
will acquire active immunity as a result of simultaneous treat- 
ment, others will not. We have no way of knowing whether any 
particular young pig or litter will acquire permanent immunity 
if simultaneous treatment is given, so we prefer to maintain the 
immunity of all young pigs with serum alone, and to finish with 
simultaneous treatment when the animals are about twelve weeks 
old. A cheaper plan than this will be available in well-kept herds 
if the findings of Niles are confirmed ; a more effective one is not 
likely to be found as long as we use serum and virus as they are 
now prepared. 



HANDLING HOG CHOLERA IN THE FIELD 173 

through an outbreak even when they are born in 
pens containing hogs sick with cholera, and this 
presents no great difficulties when the sows are 
immune, but when farrowing and recently far- 
rowed sows are susceptible, they do not tolerate 
virus well. Despite the fact that they receive 
serum a few will die, other will fail to nurse their 
litters, and on the whole results are much less 
satisfactory than they are when reasonably effec- 
tive isolation can be practiced. 

We do not wish to convey the impression that 
after hog cholera reaches a herd we can prevent, 
by isolation, ultimate infection of all the animals 
in it for exactly the reverse is true. The point 
we emphasize is that when the disease appears 
among sows that are farrowing, infection of many 
of them can be delayed by isolation, that they gain 
valuable time, and they and their litters are in 
better condition to withstand the effects of the 
virus when later it reaches them, either by natural 
means or through simultaneous treatment. A 
sow undergoing serum-virus reaction when her 
litter is a day or two old is in some danger of 
death, and even if she lives lactation may cease 
and her pigs perish. Delay the event of infection 
four weeks, and regardless of how it affects the 
sow the litter can be saved. The theoretical 
grounds for handling farrowing sows in this man- 
ner are obvious, but we recommend the plan of 



174 HOG CHOLERA 

isolation only because repeated trials have proved 
it effective. 

Establishing and maintaining a hog cholera 
immune herd. So far we have dealt with hog 
cholera after it has reached the herd. We are 
now to consider methods of preventing it from in- 
fecting the herd, which yield even better results. 
In their relation to the prevention of hog cholera, 
most herds fall into three general classes: those 
from which the virus can be excluded ; those con- 
stantly threatened with hog cholera; and pure- 
bred herds from which immune breeding stock is 
sold. The herds in the tirst class do not require 
immunization; those in the other two classes are 
best maintained immune. 

The first question to be decided when a client 
consults his veterinarian is whether it is really 
necessary for the herd to be maintained immune. 
Is hog cholera prevalent in the vicinity? Has it 
appeared periodically on the farm in question? 
Is the herd subsisting partially or wholly on gar- 
bage ? Is the breeder buying in hogs at frequent 
intervals! Does he take sows to neighboring 
farms to be bred, or are sows brought to his farm 
for the same purpose? Has he an established 
market for immune breeding stock, or does he 
wish to estabhsh one? Has the herd access to a 
stream that may be contaminated mth hog chol- 
era virus? If all these questions can be answered 



HANDLING HOG CHOLERA IN THE FIELD 175 

in the negative we should advise the breeder not to 
immunize. It is an unnecessary expense, and 
when once simultaneous treatment is employed 
in a herd there is some danger in discontinuing 
its use. Pigs thus immunized may eliminate vir- 
us, and this may be on hand to infect susceptible 
animals that subsequently are added to the herd 
by birth or purchase. In case it is desired to dis- 
continue immunization, at least four months, and 
preferably six, should elapse between the date 
when simultaneous treatment is last used on the 
place, and that of the introduction of susceptible 
recruits into the herd. All of these facts should 
be perfectly clear to the breeder before virus is 
used in his herd. 

When chances of infection with hog cholera are 
remote, and the breeder is advised against main- 
taining an immune herd, he should be cautioned 
against all the practices that may result in the in- 
fection of his swine. He should also be informed 
regarding the things that would lead him to sus- 
pect the presence of hog cholera, and the neces- 
sity for early reporting of an outbreak, should it 
occur, must be made plain. 

When hog cholera threatens ultimately to attack 
a herd and destroy it we can render the breeder 
no greater service than in advising him to main- 
tain it immune to cholera. Much as we dislike the 
idea, in the abstract, of introducing virus into 



176 HOG CHOLERA 

new territory, our experience in concrete cases is 
that one untreated cholera infected herd in a 
neighborhood is more of a menace to adjacent 
herds than ten properly maintained immune with 
simultaneous treatment. In the untreated, in- 
fected herd, there is a great temptation sometimes 
to sell animals before a diagnosis of cholera is 
made, some breeders are slow to accept the fact 
that hog cholera is in their herds, and on the 
whole the attack comes on unheralded, and much 
damage is done before its true nature is realized. 
On the other hand, when we administer simultane- 
ous treatment to a herd we deliberately establish 
our defenses against the spread of hog cholera 
that may possibly result from it, the period of 
acute danger is quickly passed, and the herd is no 
longer a menace to others in the vicinity. 

"When once the breeder decides to maintain his 
herd immune to cholera, the practice must be faith- 
fully carried out. Between keeping all animals 
immune to cholera at all times and declining to 
use any virus whatever, there is no middle ground. 
We cannot temporize with a disease like hog chol- 
era. Like the proverbial nettle, simultaneous 
treatment incident to maintaining a cholera-im- 
mune herd must be grasped firmly or avoided alto- 
gether, for it mil not do to have virus and suscep- 
tible pigs in the herd at alternate intervals. 
Sooner or later the two will get together. 



HANDLING HOG CHOLERA IN THE FIELD 177 

Let US suppose that a breeder of pure-bred hogs 
wishes to establish a trade for immune breeding 
animals, and has decided to maintain a cholera im- 
mune herd. His herd consists of two large herd 
boars, fifty brood sows nursing litters about four 
weeks old, fifty gilts recently bred and now being 
sold daily in twos and threes as the trade de- 
mands, and a herd of one hundred fattening hogs 
that will be ready for market in six weeks. Hog 
cholera is not threatening the herd. How is it 
to be handled with the greatest safety, and with 
the least expense and inconvenience? 

The brood sows are not in the best condition to 
receive simultaneous treatment, the gilts could not 
be sold and shipped at once if it were given, and 
the fattening hogs will be sold anyhow in six 
weeks. If we wait that length of time the gilts 
also will be sold, the young litters will be weaned, 
and sows and pigs will be in condition to receive 
simultaneous treatment. The two boars are thus 
the only animals in the herd for which the delay 
of six weeks is not positively indicated, and they 
can be immunized as well at one time as another. 

From this concrete example we develop the sim- 
ple rule that when choice is allowed we begin im- 
munizing at a time when the herd is at a minimum 
as far as numbers of adult breeding stock is con- 
cerned, and when the animals are in condition to 
receive simultaneous treatment with the least pos- 



178 HOG CHOLERA 

sible risk. In the average farm herd the most 
opportune time to immunize is three or four weeks 
after the spring litters are weaned. 

On the other hand, when the herd is immediately 
threatened with hog cholera we have no choice but 
to accept it as it is, and protect it at once. Under 
such circumstances the plan is to give simultane- 
ous treatment to all animals in condition to re- 
ceive it, and serum alone to the remainder. Every 
four weeks we return and repeat the process, con- 
fining the treatment to those that received serum 
alone previously, until the entire herd has received 
simultaneous treatment, and permanent immunity 
has thus been established. 

When once the adult breeding stock is immune, 
our task is then to immunize the young litters as 
they come on. This is relatively simple for the 
veterinarian and inexpensive for the breeder. 
On farms where methods of swine husbandry are 
the best, and at times when there appears to be 
little immediate danger from hog cholera, the best 
plan is to keep close watch on the pigs until they 
are about twelve weeks old and then give simul- 
taneous treatment. In many herds though, es- 
pecially the large garbage-fed herds in the East, 
a high percentage of the pigs will, if left unpro- 
tected, contract hog cholera before they reach an 
age approaching twelve weeks, and a considerable 
number that do not actually contract the disease 



HANDLING HOG CHOLERA IN THE FIELD 179 

will fail to develop so as to be fit subjects for 
simultaneous treatment. In these herds, the only 
effective plan we know of is to protect the pigs 
with serum alone until they are old enough and in 
proper condition to receive serum and virus. Un- 
der ordinary conditions the pigs receive serum 
alone when they are between three and six weeks 
of age, they are weaned when they are about 
eight weeks old and receive simultaneous treat- 
ment two to four weeks later. It is best to cas- 
trate them as sucklings. Under exceptional con- 
ditions we are compelled to give more than one 
dose of serum alone before the time is ripe for 
simultaneous treatment, but an extra dose of se- 
rum for a small pig is not expensive. 

We have used this general plan since 1912, 
starting with several garbage-fed and cholera in- 
fected herds in quarters that did not permit clean- 
ing and disinfecting, and protecting all subsequent 
litters of pigs, year after year, with losses from 
all causes totaling considerably less than five per 
cent. We know of several other veterinarians who 
have obtained like results during a term of years, 
and we do not know of a single instance where the 
plan has been followed consistently and found 
wanting. The preliminary doses of serum alone 
are not necessary in all herds, but we may resort 
to them confidently under conditions such as we 
have described. 



180 HOG CHOLERA 

Several points that contribute to the success of 
maintaining an immune herd remain to be men- 
tioned. Especially in large herds it is a good 
practice to mark each pig at the time it is immun- 
ized so that it can be positively identified. Other- 
wise we are likely to miss an occasional pig or lit- 
ter, and if these untreated animals subsequently 
contract hog cholera, we are called to account for 
deaths for which we are in no way responsible. 
We should also suggest to the breeder the advan- 
tage of breeding several sows near the same time, 
so that a considerable number of pigs can be im- 
munized at one time. In addition to economy in 
immunizing this practice enables the breeder to 
provide foster mothers for pigs farrowed by sows 
which on account of death or disease incident to 
parturition are unable to nurse their litters. 

It is important that pigs shall grow steadily and 
rapidly from birth until the time when simultane- 
ous treatment is administered. Influences that re- 
tard growth usually lower resistance as well and 
we are thus compelled to maintain the immunity 
of poorly nourished pigs with serum alone much 
longer than is necessary in handling thrifty pigs. 
Any suggestions that will aid the breeder to grow 
pigs rapidly during the first three months of their 
lives mil be greatly to his advantage. 

Handling feeding hogs. A common practice 
on farms in many parts of the country, more par- 



HANDLING HOG CHOLERA IN THE FIELD 181 

ticularly in the corn-belt, is that of purchasing 
feeding shoats in the fall of the year to consume 
the season's crop of grain. The general tendency 
is for these shoats to be raised in regions where 
land is rather cheap, and fattened in localities 
where higher-priced land compels a more inten- 
sive type of farming. Direct communication be- 
tween the breeders who raise the shoats and the 
feeders who finish them is not generally main- 
tained. The breeder seeks a seller's market in 
cities where there are large stockyards, and the 
feeder habitually goes to these places to buy. Be- 
fore the discovery of anti-hog-cholera serum, long 
years of bitter experience had taught feeders that 
hogs which pass through large public stockyards 
very often contract cholera. As soon as the serum 
was discovered it was eagerly seized on in at- 
tempts to protect stockyard shoats that subse- 
quently were to be shipped to other farms to be 
fattened. The desire was to give these animals 
permanent immunity to hog cholera, so it grew to 
be a general practice to administer simultaneous 
treatment to them in the yards, and ship them in 
the course of a few days to the feeder's farm. 
Years of experience prove that this practice, 
though perhaps an improvement over old meth- 
ods, is frequently the cause of heavy losses, both 
in the immediate animals treated and in hogs 



182 HOG CHOLERA 

with which they come in contact after they reach 
their various destinations. 

Those who follow the practice are merely lucky 
if they do not sustain heavy losses because they 
continually ignore the fact that a reaction nor- 
mally follows simultaneous treatment, and that 
shipping lowers the resistance of hogs to such 
an extent that the reaction may prove fatal. 
When we add to the effects of shipping and simul- 
taneous treatment those incident to a brief or 
prolonged stay in infected yards before the treat- 
ment is administered, as well as those that grow 
out of injudicious feeding and watering when the 
animals reach the end of a journey, fatigued, hun- 
gry, and thirsty, we have a chain of devitalizing 
influences that often cause disaster. 

It is well known also that many swine unloaded 
at stockyards do not leave home free from dis- 
ease. Oftentimes a consignment of hogs repre- 
sents a breeder 's final determination to ^ ' cash in ^ ' 
on a herd that is badly infested with parasites, 
that is suffering with some obscure respiratory 
disease, or one that has recently contracted hog 
cholera. Despite the fact that apparently well 
animals are selected from such herds for shipping 
each animal selected is potentially the source of 
future trouble. What is one to expect if in pur- 
chasing hogs for the feed-yard he chances to in- 
clude even a few individuals of this kind? The 



HANDLING HOG CHOLERA IN THE FIELD 183 

mere fact that many lots of shoats are shipped 
long distances to stockyards and after receiving 
simultaneous treatment are at once reconsigned 
to distant localities which they reach without im- 
mediate or subsequent mishap has little bearing 
on the problem as a whole. It is the fact that 
many lots of hogs will not endure such handling, 
and that we cannot always distinguish in advance 
between those that will and those that will not, 
that still troubles us. This aspect of the subject 
will receive further attention in the chapter on 
^^The Control and Eradication of Hog Cholera.'' 

Let us assume that a man living in western New 
York requires two hundred shoats as feeders. 
His natural purchaser's market is in the stock- 
yards at Buffalo, or further west in the hog-rais- 
ing districts of Ohio. He knows that there are 
certain dangers connected with shipping hogs and 
he consults his veterinarian in order to learn how 
they can be avoided. What precautions should 
he be advised to take? 

Other things being equal it is best to purchase 
direct from the farm, for this avoids unloading 
animals at large stockyards, and it is much easier 
to determine the true condition of hogs when we 
examine them in what may be termed their nor- 
mal habitat than when we inspect them hurriedly 
during the excitement and confusion that prevails 
at the average stockyard. If immune feeders can 



184 HOG CHOLEKA 

be purchased from a reliable source on the farm, 
that is by far the most satisfactory plan. In 
case that is impossible, our client should be ad- 
vised to purchase from thrifty farm herds and to 
assemble the animals on a stated day at a local 
shipping point. They should then be given serum 
alone, placed in clean comfortable well-bedded 
cars, and shipped at once to their destination. 
Wlien they arrive at the feeder's farm, they should 
be placed in dry comfortable quarters and fed 
sparingly on light foods for a few days. After 
they become accustomed to the change in feed and 
quarters — say in two or three weeks — they should 
be given simultaneous treatment. 

If circumstances compel our client to purchase 
at the stockyards, he should if possible see the 
animals unloaded, and in any event he should not 
select animals that have been in the yards several 
days. It is best to avoid mixed lots of hogs, and 
those that contain a considerable number of dead 
animals when they arrive at the yards, for these 
often are shipped to market because of disease. 
Hogs that cough persistently should not be ac- 
cepted. When once the selection is made the ani- 
mals should be given serum alone without delay 
and shipped at once to their destination. When 
they arrive at the feeder's yards they require han- 
dling similar to that accorded animals purchased 
directly from the farm. 



HANDLING HOG CHOLEKA IN THE FIELD 185 

Careful and experienced men can usually select 
satisfactory feeders in large stockyards, but on 
the whole there are unavoidable risks associated 
with the practice. 

Handling- show hogs. Show hogs constitute 
a separate problem in themselves, because they 
are of exceptional value, and because they must 
necessarily be subjected to handling entirely dif- 
ferent from that accorded the ordinary farm or 
market hog. It is not uncommon for show hogs 
to contract cholera during contact with other 
swine in the show ring or in transit from fair to 
fair, and not infrequently they arrive home appar- 
ently well, and develop symptoms of the disease 
during the few days following, thus infecting the 
entire herd which they represent. This experi- 
ence has been so common that the practice of 
showing hogs that are not immune to cholera is 
indefensible. Some fair associations require cer- 
tificates to the effect that hogs are immune to chol- 
era before they will admit them to the show ring. 

The breeder who maintains his herd immune to 
cholera has no difficulties to face from this quar- 
ter, for as far as hog cholera is concerned, he* may 
send his animals out on the fair circuit secure in 
the knowledge that they will not themselves be- 
come infected, nor be instrumental in infecting 
others with which they come in contact. 

The breeder whose herd is susceptible to cholera 



186 HOG CHOLERA 

must have his show hogs simultaneously treated 
at least thirty days before they leave for the fairs, 
or else he must give them serum alone at the 
time they start, and repeat the treatment at three- 
week intervals as long as they are on the road. 
Neither plan is entirely free from objection, but 
either is far from better than to neglect immun- 
izing. If simultaneous treatment is given this 
necessitated the introduction of virus on a farm 
where there are untreated susceptible hogs, and 
thus it is applicable only where there are facili- 
ties for effective segregation of the show hogs. 
If serum alone is given and the hogs are infected 
with cholera at the fairs they must pass through 
the resulting reaction at a time when they are low 
in resistance, and if the reaction is so severe that 
it results in virus excretion, there is danger that 
in returning from the fair circuit the show hogs 
may infect the home herd. 

If simultaneous treatment is to be given show 
animals and the remainder of the herd is to re- 
main susceptible to cholera, the following plan 
is safest: isolate the show hogs in quarters that 
will permit subsequent disinfection and give them 
serum and virus; if during the next thirty days 
none of the animals develop visible sickness, dip 
or spray them thoroughly, using 3 per cent com- 
pound cresol solution, and send them out on the 
show circuit; when they return, it is best to dip 



I 



HANDLING HOG CHOLERA IN THE FIELD 187 

them a second time before they are placed with 
susceptible hogs, and where there are facilities 
for isolating them two weeks after they return 
this should be done as an additional precaution. 
We must not lose sight of the fact that even an 
immune hog can become the intermediate carrier 
of hog cholera virus. 

Should a '^ break" appear when the show hogs 
are immunized it should be handled according 
to the plan previously outlined, and as an addi- 
tional precaution, the entire herd had best be pro- 
tected with serum. In any event, w^hen the hogs 
leave the quarters in which they are placed for 
simultaneous treatment, the pens should be care- 
fully disinfected. 

When no virus is to be used in treating the show 
animals they require serum alone at the time 
they leave home, and thereafter every three weeks 
as long as they are on the road. After they re- 
turn it is well to isolate them two weeks, after 
which they may be dipped in antiseptic solution 
and placed with the remainder of the herd. 

On the whole, a breeder who habitually places 
hogs in the show ring should maintain his entire 
herd immune to hog cholera. Under most cir- 
cumstances, when this is not done the use of serum 
alone for temporary protection is indicated, but 
under exceptional conditions, where perfect seg- 
regation is possible simultaneous treatment may 



188 HOG CHOLEKA 

be given the show animals. Not infrequently the 
practitioner has the question of immunization 
thrust on him as an eleventh-hour consideration 
just on the eve of the departure of show hogs for 
the fairs. In this event he has no legitimate 
choice but to protect the animals with serum 
alone during the period of probable exposure. 

ORDERING SERUM 

Every veterinarian in country practice is likely 
sooner or later to be called on to immunize swine 
against hog cholera, and because much immuniz- 
ing consists of emergency work, serum must be 
procured without delay. For this reason the vet- 
erinarian should establish relations with a reput- 
able laboratory near at hand so that telegraphic 
orders from him Avill be filled promptly. Because 
they cannot assume responsibility for products 
that have been in other hands, most laboratories 
will not allow credit for returned serum and virus 
and thus it is desirable to order the exact quanti- 
ties required. 

Before ordering serum the veterinarian should 

ascertain the number of hogs to be vaccinated, and 

their approximate weights. A representative list 

would appear thus: 

1 boar, weight 600 pounds 

8 sows, weight 400 pounds each 

65 pigs, weight 20 pounds each 

50 shoats, weight 60 pounds each 



HANDLING HOG CHOLERA IN THE FIELD 189 

The common tendency is to estimate weights of 
swine far too low, and this should be thought of 
in connection with every serum order. 

Before the list is completed the final question, 
**Have you any other hogsT^ should always be 
asked, for it is very annoying and very common to 
find, even after we reach a farm to do the immun- 
izing, that the owner has hogs which he has not 
mentioned because he *^ hadn't thought of having 
them immunized. '^ If a simultaneous treatment 
is to be given to any of the hogs in a herd, the 
remainder must not go long without some kind 
of immunization, and lack of sufficient serum to 
treat an entire herd may often postpone the date 
of treatment or necessitate a second call. 

When all of the hogs that are in the herd are 
listed, the veterinarian can estimate the quantity 
of serum and virus required, provided he has a 
dose table from the laboratory he patronizes. 
Lacking this, he should send in the list and allow 
the laboratory to make the estimate. 

Telegrams or letters containing orders such as 
*^ Serum and virus for 20 swine'' or ^^ Serum to 
treat a mixed bunch of 100 sows, pigs and shoats" 
are not sufficient. Every order should state the 
required quantity of each product, or it should 
include a list of the number of hogs and their 
approximate weights. 



190 HOG CHOLERA 

Most field work falls within the scope of the con- 
crete instances outlined in this chapter, but it is 
necessary, as we endeavored to make clear in the 
beginning, for one who handles hog cholera to 
understand hog cholera. Our aim throughout has 
been to show why as well as what, but if we have 
fallen short of this aim we can at least assure our 
readers that the methods recommended are con- 
servative and effective, and that they have been 
developed as a result of years of field and labora- 
tory experience. 

One final thought. The beginner in hog cholera 
work sooner or later finds himself face to face 
with some baffling situation. A herd seems in 
need of immediate protection but doubt in regard 
to diagnosis, doubt as to whether the complete 
history of the herd has been frankly laid before 
him, and the question whether complete coopera- 
tion will be accorded him in the subsequent han- 
dUng of the herd, render selection of the method 
of immunizing difficult to make. ''When in doubt 
and emergency recjuires immediate protection of a 
herd, use serum alone; then follow with simulta- 
neous treatment in less than four weeks if subse- 
quent development of the disease requires it" is 
the final caution we leave with the beginner. 



HANDLING HOG CHOLERA IN THE FIELD 191 

The Veterinarian's Charge for Serum and Its 

Administration 

If a veterinarian expects to remain long in prac- 
tice he must render service worth much more than 
the charge he attaches to it, and the benefit derived 
from his calls must be obvious to his clients. The 
fact that immunization of hogs, especially large 
herds in localities where hog cholera is prevalent, 
results in a great and obvious saving to the 
breeder has placed this phase of veterinary prac- 
tice almost in a class by itself. We do not ac- 
tually render a greater service in checking an out- 
break of hog cholera than we do in eradicating 
tuberculosis from a cattle breeder's herd, but hog 
cholera is an acute and fatal disease and the 
direct saving due to its control is far more appar- 
ent to the breeder than some other services, 
equally as valuable, that we render him. Because 
of this fact, and because of the great demand that 
has existed for the services for veterinarians in 
immunizing swine, certain abuses in regard to 
charges for serum administration have come to 
light. Complaints have been leveled at a few 
shortsighted and greedy individuals, but they have 
reacted to the dicredit of the profession as a 
whole. Especially when large numbers of hogs 
are vaccinated in one day, when charge is made by 
the head, and a profit greater than is fair is added 



192 HOG CHOLERA 

to the serum used, the veterinarian goes home 
leaving his client believing that he, and other 
members of the profession, are shameless prof- 
iteers. The natural inference is that other pro- 
fessional charges as well are exorbitant, and this, 
as all veterinary practitioners know, is not true. 
When immunization of a herd of hogs is really 
indicated and when a veterinarian does the work 
thoroughly and conscientiously, he renders a great 
and obvious service, and is entitled to a fee con- 
siderably above that which the average breeder is 
inclined to regard as fair. The breeder would be 
surprised if he knew the cost of waste, breakage, 
and overhead which the veterinarian must pay. 
We believe though, that instead of courageously 
charging fees which are actually their due, and 
which will enable them to use first-class products 
and do careful work, too many veterinarians have 
yielded to a temptation to collect their fees, un- 
known to the breeder, in the form of profit on the 
serum used. The purchase price of the serum 
sooner or later comes to light and in the absence 
of previous explanation, the breeder naturally be- 
lieves that the difference between the price the 
veterinarian pays and the price he charges his 
clients for serum is all profit. Real and imagin- 
ary abuses in this direction have led to actual and 
proposed legislation designed, on the one hand, 
to place vaccination of hogs largely in the hands 



HANDLING HOG CHOLERA IN THE FIELD 193 

of laymen, and on the other hand to fix the margin 
of profit which the veterinarian may charge, or at 
least to prevent him from concealing from his 
client the purchase price of the serum he uses. 

Legislation of the former type can result only in 
disaster to the swine industry and harm to the 
veterinary profession, but we do not believe there 
are good reasons why the purchase price of serum 
should not be known to the breeder. Obviously 
the profession puts itself in a bad light when it 
opposes legislation of this kind, unless it can justly 
be opposed on the ground that the handling charge 
proposed is not sufficient to cover costs of waste 
and breakage. Such opposition only gives sub- 
stance to the suspicion that there is something 
to conceal. It is a principle which should be ob- 
vious to all that if the veterinary profession is to 
retain exclusive rights to administer serum and 
virus it must exercise these rights in a manner to 
justify this exclusion ; and any legislative attempts 
to discipline the occasional renegade who habitu- 
ally reaps an excessive profit on serum should, 
and we believe will be, welcomed by the better ele- 
ment in the veterinary profession. 

The veterinarian's fee for his work is his own 
private concern, and the compensation he can com- 
mand depends for the most part on the skill and 
knowledge which he employs to benefit his client ; 
but the best interests of the public demand that the 



194 HOG CHOLERA 

use of serum and virus shall be placed exclusively 
in his hands, and when this is done he has not the 
same right to fix the selling price of these products 
that he has to name his o^vn fee. Use of serum 
and virus is a public trust reposed in him rather 
than a monopoly given into his hands for private 
exploitation. His profits should come from his 
work, not from the serum he uses. 

Some practitioners charge according to the num- 
ber of hogs treated, some according to the quantity 
of serum injected, and others on the basis that 
they fix fees for other calls. No system is entirely 
free from objection, but we believe that the most 
satisfactory and fair plan is for the veterinarian 
to place a value on his day's work and charge for 
vaccinating according to the time consumed in 
doing it. He is entitled to add to this a handling 
charge on the serum he uses, to compensate for 
clerical work, express, breakage, and unused prod- 
ucts that are left on his hands. Under ordinary 
conditions, if breeders pay cash, an increase of 20 
or 25 per cent over the purchase price mil take 
care of these items, but it will not be sufficient if 
credit is habitually allowed. A practitioner can 
lose more on one bad serum bill than he can collect 
as fees for several days' work. 

The practice of charging according to the time 
consumed has obvious advantages if we let our 
clients know that we are follomng it. It con- 



HANDLING HOG CHOLERA IN THE FIELD 195 

sumes less time to vaccinate a given number of 
hogs for a client who will have the animals se- 
curely penned in clean dry quarters, and plenty of 
help ready for work when the veterinarian ar- 
rives, than it does to vaccinate one-fourth that 
number for a man who awaits the veterinarian's 
arrival and then begins a frantic or leisurely 
search for gates, lumber, ropes, and other needed 
paraphernalia. A veterinarian cannot consume 
several hours in vaccinating a small lot of pigs 
and at the same time keep his fee at a figure that 
the breeder can afford to pay. The breeder who 
provides facilities and help so that the work may 
be done dexterously and rapidly should profit by 
his foresight; the one who is neglectful must ex- 
pect to pay for his negligence. 

Emergency hog cholera practice, that is, the 
care of herds already infected, will come regularly 
to a man who handles it with only a fair degree 
of effectiveness. Under such circumstances even 
average veterinary service is far better than none. 
The same rule does not apply in maintaining im- 
mune herds, the phase of hog cholera control that 
offers greatest satisfaction to both practitioner 
and breeder. If the breeding in a herd is so or- 
dered that a large number of pigs can be vaccin- 
ated at one time, if the animals are grown rapidly 
and conditioned so that they will withstand simul- 
taneous treatment at an early age, and if the 



196 HOG CHOLERA 

breeder habitually provides facilities that allow 
vaccinating to be done without loss of time, the 
cost per head can be kept at a minimum. The 
veterinarian who so advises his clients as to bring 
these things about is the only one who can hope 
to enlarge his swine practice and gain lasting 
success in hog cholera work. A system of wireless 
which we do not completely understand, but whicn 
nevertheless spreads intelligence rapidly and un- 
erringly in country districts, will, in each veterin- 
arian's community ultimately convey the news 
that immunizing pays, or that it does not pay ; and 
the veterinarian must have it whispered abroad 
that immunizing their herds pays his clients or 
he will ^'kill the goose that lays the golden egg.^' 



CHAPTER X 

HOG CHOLERA, MEAT INSPECTION AND GARBAGE 

FEEDING 

Hog cholera is a widespread disease affecting 
just one species of animal used solely to produce 
meat for human food, and its status as far as meat 
inspection is concerned is necessarily well estab- 
lished. The following paragraphs from Edel- 
mann^ set forth the broader principles which gov- 
ern the formulation of more detailed and specific 
regulations which are in force in various abattoirs 
throughout the country: 

*^ Judgment of the meat in swine erysipelas swine 
plague and hog cholera. In view of the fact that meat 
of these diseased animals has frequently been eaten for 
food without ever having incurred any impairment or 
injury to man, it can hardly be classed as injurious to 
health. In individual cases however the following should 
be considered : 

**1. The entire carcass is unfit for food as soon as 
marked substantial changes (congestion of blood, serous 
infiltration, degeneration, yellow discoloration) of the 
musculature or fatty tissue are observed or when marked 
emaciation has occurred. 

^Edelman, Meat Hygiene (English translation by Mohler and 
Eichhorn; 2d edition, 1911). 

197 



198 HOG CHOLERA 

''2. In all other cases, with the exception of the 
chronic forms of swine plague and the sequelae of this 
disease and those of hog cholera, the carcass in all of 
these diseases is to be considered fit for food but subject 
to certain conditions. For veterinary sanitary reasons, 
and partly in consideration of the causative agents in 
the blood of swine erysipelas, swine plague and the acute 
forms of hog cholera, the meat and fat are to be boiled, 
steamed (rendered into lard) or pickled. The portions 
affected by the disease should be condemned. 

*'3. In case of slow chronic forms of swine plague 
without disturbance of the general condition, or sequelae 
of this disease (adhesions, cicatrices, capsulated caseated 
areas etc.) or of hog cholera (caseation of mesenteric 
lymph glands, adhesions of intestines, formation of cica- 
trices in the intestinal mucosa) only the affected portions 
of the meat are to be condemned and destroyed. The 
remainder of the carcass is fit for feed without any re- 
striction. ' ' 

It will be observed that swine plague and swine 
erysipelas are governed by the same general con- 
siderations that apply to hog cholera. In view of 
the fact that swine plague occurs most frequently 
as a complication of hog cholera as well as of the 
fact that rapid differentiation of all three dis- 
eases based on abattoir examinations alone is not 
possible, it is fortunate indeed that these diseases 
run so nearly parallel in their relation to meat 
inspection. 

From the excerpt from Edelmann we glean the 
following essential considerations: first, the fit- 
ness of the meat for human food is based on patho- 



HOG CHOLERA AND MEAT INSPECTION" 199 

logical changes in the meat itself, and is not deter- 
mined by the probable presence or absence of the 
causative agents of hog cholera, swine plague or 
swine erysipelas ; second, carcasses of hogs which 
before slaughter were obviously suffering with 
any one of the three diseases, may, in the absence 
of extensive pathological changes in the meat it- 
self be passed for human food, but for veterin- 
ary sanitary reasons it should be boiled, rendered 
or pickled in order to destroy causative agents of 
either of the three animal diseases which it may 
contain. 

A review of these facts leads logically to the 
conclusion that as far as hog cholera is concerned 
there is, and can be, no sharp line of demarcation 
between carcasses that are fit for human food and 
those which are unfit, because it has not been 
shown that hog cholera virus is injurious to man. 
The more important phase of meat inspection as 
it applies to hog cholera centers around the de- 
cision which determines whether a particular car- 
cass requires special treatment (boiling, render- 
ing or pickling), in order that parts of it may not 
subsequently infect other swine. Edelmann states 
clearly the need for a distinction between the fit 
and the unfit based solely on veterinary sanitary 
reasons, but he is silent as to how this distinc- 
tion is to be made. 

The IT. S. Bureau of Animal Industry meat in- 



200 HOG CHOLERA 

spection regulations are much more specific in 
regard to the manner in which the distinction be- 
tween the fit and the unfit shall be drawn, but the 
distinction is based wholly on considerations deal- 
ing with the fitness of the meat for human food. 
Veterinary sanitary considerations, which would 
include atempts to require cooking or rendering 
of all carcasses which contain hog cholera virus, 
do not enter in. The parts of these regulations 
which refer specifically to hog cholera read as fol- 
lows: 

''Reflation 9, section 2, paragraph 2. All hogs 
plainly showing on ante-mortem inspection that they are 
affected with either hog cholera or swine plague shall be 
marked 'U. S. condemned' and disposed of in accordance 
with section 8 of this regulation. 

''Regulation 9, section 2, paragraph 3. If a hog has 
a temperature of 106° F. or higher, and if it is of a 
lot in which there are symptoms of either hog cholera 
or swine plague, in case of doubt as to the cause of the 
high temperature, after being marked for identification, 
it may be held for a reasonable time, under supervision 
of an inspector, for further observation and taking of 
temperature. Any hog so held shall be reinspected on 
the day it is slaughtered. If upon such reinspection, 
or, when not held for further observation and taking of 
temperature, then on the original inspection, the hog has 
a temperature of 106° F. or higher, it shall be condemned 
and disposed of in accordance with section 8 of this 
regulation. 

"Regulation 9, section 2, paragraph 6. All animals 
which, on ante-mortem inspection, do not plainly show, 
but are suspected of being affected with, any disease or 



HOG CHOLEEA AND MEAT INSPECTION 201 

condition that, under these regulations, may cause con- 
demnation, in whole or in part, on post-mortem inspec- 
tion, shall be so marked as to retain their identity as 
suspects until final post-mortem inspection, when the car- 
casses shall be marked and disposed of as provided else- 
where in these regulations, or until disposed of in ac- 
cordance with section 7 of this regulation. 

**Eegulation 9, section 4, paragraph 1. All hogs, even 
though not themselves marked as suspects, which are of 
lots one or more of which have been condemned or 
marked as suspects under section 2 of this regulation 
for either hog cholera or swine plague, shall so far as 
possible be slaughtered separately and apart from all 
other animals passed on ante-mortem inspection. 

*' Regulation 9, section 7, paragraph 3. A hog sus- 
pected of being affected with hog cholera or swine plague 
may be set apart and held, under bureau supervision, 
for treatment with anti-hog-cholera serum. If at the 
expiration of the treatment period the animal upon 
examination is found to be free from disease it may be 
released for any purpose. 

''Regulation 9, section 8. Except as hereinafter pro- 
vided in this section, animals marked 'U. S. condemned' 
shall be killed by the establishment, if not already dead, 
and shall not be taken into an establishment to be 
slaughtered or dressed ; nor shall they be conveyed into 
any department of the establishment used for edible 
products; but they shall be disposed of and tanked in 
the manner provided for condemned carcasses in regula- 
tion 14. The 'U. S. condemned' tag shall not be re- 
moved from, but shall remain on, the animal when it 
goes into the tank. The number of such tag shall be 
reported to the inspector in charge by the bureau em- 
ployee who affixed it, and also by the bureau employee 
who supervises the tanking of the animal, provided, 
that any animal condemned on account of hog cholera 
and swine plague, as prescribed in paragraph 1, 2, 



202 HOG CHOLEEA 

or 3 of section 2 of this regulation, may be set apart 
and held, under bureau supervision, for treatment with 
anti-hog-cholera serum, the requirement that such ani- 
mal shall be killed shall be held in abeyance to await 
the result of the treatment. If at the expiration of 
the treatment period the animal upon examination is 
found to be free from disease, the 'U. S. Condemned' 
tag shall be removed and the animal released for any 
purpose." 

Post-mortem inspection. 

''Kegulation 11, section 4, paragraph 1. The car- 
casses of all hogs marked as suspects on ante-mortem 
inspection shall be given careful post-mortem inspection ; 
and if it appears that they are affected with either acute 
hog cholera or swine plague they shall be disposed of 
in accordance with paragraph 2 of this section. 

'* Regulation 11, section 4, paragraph 2. Carcasses of 
hogs that show acute and characteristic lesions of either 
hog cholera or swine plague in any organ or tissue, other 
than the kidneys or lymph glands, shall be condemned. 
Inasmuch as lesions resembling those of hog cholera or 
swine plague occur in the kidneys and lymph glands of 
hogs not affected with hog cholera or swine plague, 
carcasses of hogs in the kidneys or lymph glands of 
which appear any lesions resembling lesions of hog chol- 
era or swine plague — shall be carefully further in- 
spected for corroborative lesions. On such further in- 
spection — 

''(a) If the carcass shows such lesions in the kid- 
neys, or in the lymph glands or both, accompanied by 
characteristic lesions in some other organ or tissue, 
then all lesions shall be regarded as those of hog cholera 
or swine plague, and the carcass shall be condemned. 

"(&) If the carcass shows in any organ or tissue, 
other than the kidneys or lymph glands, lesions of either 



HOG CHOLEKA AND MEAT INSPECTION 203 

hog cholera or swine plague which are slight or limited 
in extent, it shall be passed for sterilization in accord- 
ance with regulation 15. 

** (c) If the carcass shows no identification of either 
hog cholera or swine plague in any organ or tissue other 
than the kidney or lymph glands it shall be passed for 
food unless some other provision of these regulations 
requires a different disposal." 

For years it has been a common practice among 
swine raisers to consign hogs to market as soon as 
hog cholera appeared among them, and even at 
the present day, when an effective preventive of 
the disease is at hand, the custom still prevails. 
If an entire herd consists of hogs nearing com- 
pletion of the fattening period, and if cholera is 
recognized as soon as it appears, the loss to the 
feeder is not heavy. He promptly markets all 
hogs that are apparently well, leaving behind the 
few that are visibly sick. If, though, a herd in- 
cludes sows, pigs and shoats which cannot be mar- 
keted to advantage, or if it consists of pure-bred 
animals, heavy and unnecessary loss must be ac- 
cepted in consigning it to market. Unfortunately 
the loss is not confined to the man who ships the 
infected hogs. His herd becomes a menace to 
others in the vicinity as it is driven to the nearest 
loading station, and it helps to perpetuate the in- 
fection which, existing in practically all large pub- 
lic stockyards in the country, threatens all cholera 
susceptible swine not intended for immediate 



204 HOG CHOLERA 

slaughter. Nor is the danger terminated when 
the hogs reach the shambles. An impression pre- 
vails that in establishments where meat inspec- 
tion regulations are in force, carcasses that con- 
tain hog cholera virus are condemned, and those 
that do not contain it are passed for food. This 
is not the case. Many carcasses that contain the 
virus readily pass inspection, and although they 
are perfectly fit for human food, trimmings from 
them regularly find their way into garbage, and 
when this is fed to susceptible hogs, they, in turn, 
contract disease. It is a vicious cycle, and one 
very difficult to break. 

When a consignment of hogs from a cholera 
infected herd reaches an establishment where fed- 
eral meat inspection regulations are in force it is 
first subjected to ante-mortem inspection. With 
respect to hog cholera it may contain five classes 
of hogs: first, dead hogs; these are condemned 
and tanked: second, hogs that show undoubted 
symptoms of cholera; these also are condemned 
and tanked: third, those that show suspicious 
symptoms and temperatures below 106° F., these 
are slaughtered; carcasses that show hog cholera 
lesions are condemned or passed for sterilization 
according to the extent of the lesions; those that 
show no lesions are passed for food : fourth, hogs 
apparently normal, and those which show suspi- 
cious symptoms, having temperatures above 106° 



HOG CHOLERA AND MEAT INSPECTION 205 

F. ; these are condemned or isolated for further 
temperature records; in case further tempera- 
tures are taken the animals are condemned if the 
readings are still above 106°; otherwise they fall 
into class three or class five : fifth, apparently nor- 
mal hogs that show temperatures below 106°; 
these pass ante-mortem inspection and post-mor- 
tem as well if they do not show lesions of hog chol- 
era in organs other than the kidneys or lymph 
glands. 

Let us consider the individual hog. Briefly 
stated, the requirements in order that it may pass 
inspection are that it shall not show conclusive 
symptoms of hog cholera, it shall not show sus- 
picious symptoms plus hog cholera lesions, it shall 
not maintain repeated temperature readings above 
106° F., and regardless of ante-mortem findings 
the carcass shall not on post-mortem show hog 
cholera lesions in organs other than the kidneys or 
lymph glands. What are the chances for car- 
casses that contain hog cholera virus to pass in- 
spection? 

This question is best answered by considering 
the average case of hog cholera. Let us suppose 
that a hog becomes infected to-day. According to 
Dorset, ^^ Repeated experiments have sho^\^l that 
the blood of pigs that have previously been in- 
oculated with the virus of cholera becomes infec- 
tious for others within twenty-four hours; the 



206 HOG CHOLERA 

urine and feces contain the virus usually in forty- 
eight hours, and the secretions of the eyes and 
nose become infectious by the third day follow- 
ing infection: therefore these experiments show 
that infected pigs are capable of transmitting 
the disease before they themselves show any visi- 
ble illness. '^ ^ 

Thus the blood and therefore the meat of a hog 
infected to-day will to-morrow contain hog cholera 
virus sufficient to infect others, but there will be 
neither symptoms, temperature readings nor le- 
sions to cause its condemnation. The same will 
be true on the second, third and fourth days fol- 
lowing infection, but from that time on we may at 
any time expect developments that would cause 
condemnation. These may, though, be delayed 
several days longer. There is a time, at least 
three days on an average, in the lives of practi- 
cally all hogs affected with acute hog cholera when 
they ivill pass inspection and when hits of porTc 
from their carcasses ivill infect other sivine to 
which they are fed. This interval varies from 
one or two to several days, and is measured, 
roughly, by the time required, after the first 
twenty-four hours following infection, for the 
temperature to rise to 106° F., or for conclusive 
symptoms or extensive cholera lesions to appear. 

^ Keport of the chief of the U. S. Bureau of Animal Industry 
for the year ending June 30, 1917, 



HOG CHOLERA AND MEAT INSPECTION 207 

With these facts in mind, let us again consider 
the farm herd from which cholera infected hogs 
are shipped. Often a considerable number must 
die before the owner will admit, even to himself, 
that he is dealing with hog cholera. Then there 
is the delay incident to securing transportation, 
and there are many hours during which infected 
and sound animals are crowded together in a stock 
car. Finally, after the hogs reach the yards there 
is an additional delay of several hours or even 
several days before they are killed. x\ny person 
familiar with hog cholera knows that in such a 
consignment a great majority of the hogs become 
infected before they are killed and any person 
familiar with present-day meat inspection regula- 
tions knows that under such circumstances the 
vast majority of the infected animals will pass in- 
spection. The hogs have every chance to become 
infected but the disease does not have time to 
develop sufficiently to cause their condemnation. 

The practice of marketing swine herds as soon 
as cholera appears is no longer necessary. It 
rarely profits the man who follows it, and it per- 
petuates hog cholera, working great harm to the 
smne industry. Before the discovery of protec- 
tive serum a herd of hogs once infected with chol- 
era became a total loss unless some of the animals 
could be salvaged by slaughter. With the plenti- 
ful supply of serum now available an infected herd 



208 HOG CHOLERA 

can safely and profitably be kept at home. All 
that is required is prompt reporting, prompt diag- 
nosis and prompt serum treatment. With few 
exceptions serum will, at any given time, save all 
hogs which are not at that time already danger- 
ous carriers of hog cholera virus. 

In the United States, during the decade ending 
in 1911 approximately 18,000 hogs were condemned 
annually on account of hog cholera. In 1914 
the number reached a total of 116,000; in 1917, 
33,000. According to Bureau of Animal Industry 
estimates, 40 per cent of the pork which is killed 
and 15 per cent of that which is marketed in the 
United States is slaughtered on farms or in abat- 
toirs in which no inspection is maintained. Judg- 
ing from my study of the situation as a whole, my 
belief — which I would be reluctant to express in 
concrete terms if it were not essential to convey at 
least an approximate idea of existing conditions — 
is that in the country at large, for each hog which 
is condemned for cholera, at least three virus-con- 
taining carcasses pass or evade inspection. What 
becomes of them subsequently? 

Each infected carcass possesses almost infinite 
possibilities in regard to its final distribution. 
Whether the pork reaches the consumer in the 
form of hams, shoulders, or bacon, or whether it 
is fresh, refrigerated or cured, we should not lose 
sight of the fact that it actually contains unlabeled 



HOG CHOLERA AND MEAT INSPECTIOTC 209 

hog cholera virus, and that uncooked portions of 
it fed to susceptible hogs will produce cholera. 

Of the various preserving and preparing proc- 
esses to which pork is subjected before being 
sent to the consumer, only one that we know of — 
cooking — is certain to destroy hog cholera virus 
which it may contain. According to extensive 
experiments ^ which we have carried out the virus 
lives in fresh meat until decomposition sets in, it 
is not affected by prolonged refrigeration, and a 
representative sugar curing and smoking process 
killed it in only 43 per cent of the tests made. 

So far we have dealt chiefly with the facts sur- 
rounding hog cholera and meat inspection as they 
have been determined by exact scientific methods 
and recorded data. It remains to be added that 
clinical observations are entirely in accord with 
these facts. We hear of one outbreak of hog chol- 
era in Canada, and it is traced to a consignment 
of infected hams ; we hear of another in a remote 
lumber camp in the Adirondacks where hogs are 
kept to consume the kitchen refuse; and of still 
another on an inaccessible farm in Nevada follow- 
ing purchases of market pork. These are merely 
representative instances. At least 90 per cent of 
the outbreaks we encounter in New York can be 
traced to no other source than infected pork trim- 

* Eeport of New York State Veterinary College 1915-1916, page 
60. 



210 HOG CHOLERA 

mings in garbage, and in other Eastern states 
the situation is essentially the same. Torrance ^ 
reports similar conditions in Canada. In the 
Southern and central states a much smaller pro- 
portion of herds become infected through the 
agency of pork trimmings from carcasses that 
contain hog cholera virus, but even in these sec- 
tions there is ample evidence that the first infec- 
tion in many outbreaks takes origin in this man- 
ner. Once established in territory that supports 
a dense swine population, the disease spreads 
rapidly through many other agencies. 

Meat inspections in field outbreaks of hog 
cholera. The practicing veterinarian who is 
called to handle a farm herd infected with hog 
cholera very frequently is questioned regarding 
killing and marketing all animals that remain ap- 
parently well. How is he to advise his clients? 

Disregarding, for the moment, legal and sani- 
tary considerations, and thinking only of the plan 
that will cause our clients the least immediate 
financial loss, w^e will find relatively few instances 
where immediate slaughter can be advised. 
These occur principally in herds of feeders about 
ready for market anyhow, and in herds in which 
the disease has progressed so far that protective 
serum otfers very little hope. In either case the 

* * ' Garbage Feeding in Eelation to the Control of Hog Cholera, ' ' 
Journal of the American Veterinary Medical Association, Octo- 
ber, 1921, p. 22. 



HOG CHOLEKA AND MEAT INSPECTION 211 

hogs are worth more as pork than they will ever 
again be worth on foot, but here legal and sanitary 
considerations enter in, and it is only where the 
state law provides for slaughter under inspection 
and where provision can be made to minimize the 
danger to other herds that may result from mar- 
keting the pork, that slaughtering is to be ad- 
vised. 

New York, for instance, has a law which permits 
killing under inspection from herds infected with 
cholera, but it is only at institutions and on farms 
where the pork will not be placed on the open mar- 
ket that we have advised such a course. We hab- 
itually follow the plan of explaining the situation 
to our client, and informing him that he has a 
legal right to kill, but that he has at the same time 
a moral obligation to protect his neighbor. When 
we offer at the same time the alternative of serum 
treatment, giving a prognosis as nearly exact as is 
possible, there are few who will not decide to use 
serum or who will not profit by doing so. Indeed 
in just one instance that we recollect has one of 
our clients elected to take shelter under the law 
and disregard his neighbor. This man had a herd 
consisting originally of about four hundred hogs. 
Cholera appeared, but he refused to accept our 
diagnosis. Finally when his herd had dwindled to 
about one hundred and fifty animals, he decided to 
vaccinate. It was a forlorn hope, but we began 



212 HOG CHOLERA 

taking temperatures, intending to administer se- 
rum only to those that showed readings below 104"^ 
F. After numerous trials in which we found but 
a negligible number of readings below 106° F., we 
gave up the attempt and returned home. Later 
we were informed from reliable sources that imme- 
diately on our departure about seventy-five hogs 
from the herd were shipped to market and that the 
majority of them passed federal inspection.^ The 
man in this instance received more for the hogs 
than he would have received had he administered 
serum to all of them as an eleventh-hour mea- 
sure, but he received infinitely less than would 
have fallen to his lot had he treated the herd mth 
protective serum at the time when he was first 
warned of the danger. 

In those instances in which the practicing veter- 
inarian is called to inspect hogs that are being 
slaughtered from cholera-infected herds, the fed- 
eral meat inspection regulations ^ should be se- 
lected as a convenient guide, but unless it is so 
specified by state law, they are not to be regarded 
as inflexible or final. The practitioner must 

* This must not be construed as a criticism of the administration 
of the federal meat inspection regulations. It is merely a rather 
striking example of the fact that the regulations, admirably 
formulated and enforced to protect human health and human life, 
cannot be relied on to eliminate from our markets swine carcasses 
that contain hog cholera virus. 

^ The paragraphs that relate to hog cholera appear near the 
beginning of this chapter. 



HOG CHOLEEA AND MEAT INSPECTION 213 

adapt his decisions to the conditions under which 
he is working. If he knows that the pork is to be 
sold in the open market where it will become the 
potential cause of future outbreaks, he cannot be 
justly criticized if he is relatively severe in his 
decisions ; on the other hand, if the pork is to be 
retained at the place where it is killed, as it is on 
some institution farms, for instance, rather ex- 
tensive hog cholera lesions should be required in 
order to condemn. Carcasses that are not deemed 
fit for pork can be partially salvaged in the form 
of lard. 

When slaughter on the farm is decided on, 
ante-mortem inspection should consist first of ob- 
serving the hogs before they are disturbed, and re- 
jecting any that obviously are suffering with hog 
cholera. Then temperatures may be taken of 
those that remain and any that show readings 
above 106° F. should be condemned or put aside 
for subsequent readings. Later if they show tem- 
peratures below 106° F. they may be slaughtered 
and post-mortem findings will determine whether 
the carcass shall be passed or condemned. In case 
the weather is very warm, or if it is necessary 
to excite the animals unduly in taking tempera- 
tures, one may secure more accurate information 
by giving them a limited quantity of feed and re- 
jecting those that do not remain at the trough and 
eat greedily. Nearly all will come to the trough at 



214 HOG CHOLEEA 

first, but those that are suffering most with chol- 
era will soon return to the nest. 

Principles governing post-mortem inspection 
have already been discussed. Briefly, extensive 
changes in the meat or fat should cause condemna- 
tion. Hog cholera lesions in the kidneys and 
lymph glands do not condemn the carcass, al- 
though in cholera-infected herds such lesions prac- 
tically always establish its status as a virus car- 
rier. Carcasses that show hog cholera lesions in 
the kidneys, lymph glands and other organs as well 
are not used for pork, but if the lesions are slight 
in extent the fat may be rendered into lard. Most 
hogs that appear well on foot pass post-mortem 
inspection as well. 

Garbage Feeding 

Intimately bound up with meat inspection as it 
applies to hog cholera is the subject of garbage 
feeding. As we have already shown this prac- 
tice is the final link in the chain which is respon- 
sible for the introduction of cholera into so many 
herds of hogs. If meat inspection regulations be- 
come more stringent, garbage feeding becomes 
less hazardous; if they become less stringent, or 
if they are neglected altogether the risks from in- 
fected pork trimmings in garbage increase. In 
any event, chance alone decides when any partic- 



HOG CHOLERA AND MEAT INSPECTION 215 

ular herd that subsists on garbage will contract 
hog cholera. The larger the herd, the greater 
the supply of garbage necessary to maintain it, 
and the more certain it is to become infected. 

In earlier years feeding garbage to hogs has 
produced the most surprising and contrasting re- 
sults. Its feeding value has long been well known, 
and men who were tempted to utilize it in feeding 
hogs usually began the practice on a small scale. 
If hog cholera did not happen to reach the herd 
during the first year, the financial returns were 
usually gratifying beyond expectations, and the 
hog raiser enthusiastically increased the size of 
his herd — at the same time multiplying its chances 
to become infected with cholera. Thus a common 
experience was for the breeder to have the savings 
of one or more years invested entirely in hogs 
when cholera finally reached his herd and de- 
stroyed it. 

Various preventives of the disease incident to 
garbage feeding were advertised, and magic for- 
mulas were passed around by word of mouth. 
Perhaps one man fed salt and sulphur to his hogs 
and did not lose a single one; another neglected 
to do this and his entire herd was destroyed. 
Could any proof be more convincing! But the 
law of chance was still in operation, and hog chol- 
era was relentlessly striking down one herd after 
another, including those which received the lauded 



216 HOG CHOLERA 

preventives with those that did not, in a wholly 
impartial manner. 

There was a belief that garbage in itself pro- 
duced the disease, and there was divided opinion 
as to whether it was dietetic in nature or whether 
it was really hog cholera. The trouble was 
thought by some to be due to a variety of causes — 
as in truth it was to a limited extent — but when 
anti-hog-cholera serum was brought into use it 
was found that this product prevented most rap- 
idly-fatal infectious disease which had formerly 
plagued the garbage feeder's herd. Also the ad- 
vent of kitchen sinks and drains eliminated soap 
poisoning due to dish water which was formerly 
included in garbage. These two advances have 
placed garbage feeding on a relatively safe 
basis. 

The collection and disposal of city garbage is 
a complex and exacting process, and staggering 
sums are paid annually for this service. Disposal 
plants cost huge sums of money as original invest- 
ments, and coal, labor and upkeep incident to their 
operation require a heavy and continuous outlay. 
One city of 100,000 that we know of — and it is no 
exception — was until recently incurring the ex- 
pense of collecting its garbage and hauling it three 
miles to a disposal plant, and it was also operating 
the plant at an annual expense of $40,000. The 
garbage was burned and there was no salvage, as 



HOG CHOLEKA AND MEAT INSPECTION" 217 

there is in some disposal plants, in the form of 
grease, tankage and bones. 

Viewing the subject of garbage feeding from 
the standpoint of the mmiicipality it may be said 
that in cities of less than 100,000 feeding is by 
far the most economical plan of disposal, and ex- 
perience will probably prove that the same rule 
holds good for larger cities. If provisions are 
made for feeding, no city of less than 100,000 
should find it necessary to pay disposal costs, and 
many should be able to offset in some degree, 
collection costs as well. Cities that elect to dis- 
pose of their garbage by feeding may maintain 
piggeries as a municipal function, or they may 
provide by contract for collection and disposal. 
We believe the most satisfactory plan is for the 
city to collect the garbage and deliver it to the 
contractor's piggery or to a specified loading 
station. 

Long term contracts with optional renewals on 
the part of the contractor are the only ones that 
will prove satisfactory when the plan is to feed 
the garbage. No man can afford to build adequate 
quarters for large numbers of hogs unless there is 
assurance of a constant supply of feed during a 
term of years. Short term contracts are respon- 
sible in large measure for the fact that the gar- 
bage feeder's establishment is so often a public 
nuisance. He does not have time to organize his 



218 HOG CHOLEEA 

feeding operations, he cannot invest in good equip- 
ment that will have to be sold at a loss as soon as 
his contract terminates, and there is not sufficient 
time for the enterprise itself to yield profits that 
may be returned to it in the form of equipment. 

When a city wishes to let its garbage contract 
to the best advantage it should agree to give the 
contractor all the municipal garbage, and it should 
provide ordinances that require its drainage and 
the exclusion of tin cans, broken bottles and the 
like. Collections should be required at least once 
a week in winter and twice in summer. A five- 
year contract which the contractor can renew at 
his option if he discharges his obligations, is satis- 
factory, and will serve to entice reliable con- 
tractors. 

Municipal piggeries are successful sometimes, 
but changing city administrations are not always 
to their best advantage. Sooner or later self- 
styled ^'business men" are likely to be charged 
with their general supervision, and in formulat- 
ing business rules for their subordinates they 
themselves are likely to ignore essential natural 
laws governing swine husbandry and the handling 
of s^^ine diseases. Business principles must of 
course be observed, but they must be made to 
dovetail with principles that conserve the health 
of the swine and provide each day for their intelli- 
gent care. 



I 



HOG CHOLEEA AND MEAT INSPECTION" 219 

Garbage varies greatly in feeding value, but as 
a very general rule one ton of well drained city 
garbage which is free from extraneous matter will 
feed about fifty or sixty fattening hogs^ causing 
them to gain from % to one pound each. In other 
words one ton of garbage should produce about 
fifty pounds of pork. At least 200 pounds of a 
good grain ration is required to produce the same 
gains. Thus as far as the public at large is con- 
cerned dumped or burned garbage represents a 
great and avoidable waste, and in states with 
large urban populations this waste assumes huge 
proportions. 

Veterinary Supervision of Garbage-Fed Herds 

Herds of hogs fed on city garbage are con- 
stantly threatened with cholera, and for this rea- 
son they sooner or later come under the veteri- 
narian's care. The dangers nowadays are fre- 
quently known in advance and hence professional 
advice is sought before a herd is assembled, but 
many feeders are still ignorant of the chances they 
assume, and still others procrastinate in regard 
to immunizing. 

When a veterinarian is consulted before a herd 
is assembled, or before hog cholera appears in it 
he can render service of a high order if he is fa- 
miliar with disease prevention and swine hus- 
bandry methods. He also assumes considerable 



220 HOG CHOLEKA 

responsibility, for, given a clean herd he is sup- 
posed to know how to keep it clean. The preven- 
tion or handling of hog cholera in herds fed on 
garbage is not different in principle from han- 
dling the disease in other herds, but there are 
several difficulties peculiar to the garbage-fed 
herd that must be overcome. These difficulties are 
so closely linked up mth methods of swine hus- 
bandry that all must be considered at the same 
time. 

Should the garbage feeder raise or purchase 
feeding hogs? Many considerations enter in, but 
as a general rule if the herd is to be relatively 
small, say less than 500, if there is provision 
for exercise and a little pasture, if warm farrow- 
ing pens can be provided, and if a supervisor who 
thoroughly underctands swine breeding can be se- 
cured, the "'^est plan is to raise the pigs. Under 
ordinary conditions, as the herd is increased in 
size, raising the pigs becomes relatively less feas- 
ible. The question of loroximity to a good mar- 
ket for good feeding shoats likewise must be con- 
sidered, and what we have said in a preceding 
chapter in regard to handling feeder hogs, applies 
here as well. Shoats that have been immunized 
on the farm are by far the safest purchase, and 
susceptible ones that can be purchased from 
thrifty farm herds may be immunized without 
much danger. Purchase of stockyard hogs is ad- 



HOG CHOLERA AND MEAT INSPECTION 221 

visable at times, but judicious selection and care- 
ful handling are essential, and even then the best 
professional care does not always insure against 
considerable loss from hog cholera and its com- 
plications. 

When it is desirable to purchase feeding shoats 
to consume garbage, those weighing between 75 
and 120 pounds are most desirable. Although it 
is feasible to raise the very best pigs on garbage 
alone, the fact remains that often they begin to 
eat it well and put on rapid gains only after they 
have attained considerable size. It is likewise 
true that shoats cannot be put on full feed as rap- 
idly when garbage is fed as they can when their 
ration consists of grain, hence it is well to pur- 
chase rather light shoats so that the loss of time 
in getting them started can be made up by a rela- 
tively long fattening period. 

Except when cholera immune shoats are pur- 
chased from the farm it is necessary that immu- 
nizing shall take place before or immediately 
after they reach the feeder's yards, and thus they 
must often undergo the resulting reaction before 
the condition known in the fattening pen as ^'full 
feed'' is reached. Special care is necessary not 
to overfeed at this time. Efforts to crowd the 
animals beyond their capacity may aid in caus- 
ing ^^ serum breaks," and do injury that will re- 
quire weeks to overcome. With this one special 



222 HOG CHOLERA 

precaution our readers are referred to the head- 
ing in the last chapter entitled '^ Handling Feeder 
Hogs/' 

It is in raising pigs entirely on garbage that 
the greatest care is required. Numerous pitfalls 
are in the path of the beginner, and it is a quite 
general rule that one serious disaster is necessary 
to impress him with the necessity for avoiding 
neglect. The critical period in a pig's life is from 
weaning time until he reaches a weight near 75 
pounds. When garbage is to be the sole feed it 
is a great mistake, and a common one, for the pigs 
to be weaned while they are very young. The 
breeder is anxious that the sow shall produce an- 
other litter as soon as possible, and thus it is not 
uncommon for weaning to take place when the 
pigs are four weeks old, or a trifle more. They 
are then too young to gain well on garbage alone 
and they are subject to various dietary troubles 
that are not often observed in pigs weaned later 
in life. One good litter a year born quite early in 
the spring and nursed until the pigs are eight or 
even twelve weeks of age is more profitable than 
two litters weaned too young. However when 
warm farrowing pens are provided it is not neces- 
sary to choose between one litter a year, and two. 
The sow can nurse her litter the required time 
and then be bred at the first period of heat fol- 



HOG CHOLERA AND MEAT INSPECTION 223 

lowing weaning of the pigs regardless of the time 
of year that farrowing will occur. 

When the pigs are weaned too young *^ runts'' 
are common among them, and in waiting for the 
animals to become of sufficient size to receive si- 
multaneous treatment it is not uncommon for the 
breeder to prolong to a dangerous degree the in- 
terval between serum alone and simultaneous 
treatments. The passive immunity due to the 
former partially disappears, and hog cholera, fre- 
quently of an atypical and subvirulent type, some- 
times appears among them. Often this type of the 
disease is not recognized as hog cholera. Pigs in 
large herds require earlier serum alone treatment 
and are more likely to require two treatments 
prior to the final serum-virus administration than 
are those in smaller herds. This is because of the 
fact that in large herds the chances for infection 
are so great that the virus of the disease must be 
regarded as being continuously present. 

Pasture and abundant room for exercise are of 
great benefit to young pigs that subsist on gar- 
bage. There seems to be a general fear that pigs 
mil ' ' run all the fat off them ' ' if they are allowed 
generous room for exercise. We have repeatedly 
observed the effects of turning pigs from cramped 
and dirty quarters into pastures or large enclos- 
ures, and the change has always been in their 



224 HOG CHOLERA 

favor. Granting good weather conditions, very 
young pigs that become exhausted in attempts to 
follow the sow, and feeders near completion of 
the fattening period are the only exceptions to 
this rule. 

There is a tradition that hogs grown on garbage 
from generation to generation become accustomed 
to it and consume it to better advantage. For- 
merly we were inclined to regard this belief as 
being without foundation on fact, but in later 
years we have seen evidence that causes us to 
change our views. It is certain that sows pur- 
chased from grain-fed herds and required to sub- 
sist on garbage frequently fail to farrow large 
litters in the spring subsequent to the change, and 
while this may often be explained on the ground 
of insufficient exercise and overfat condition, this 
explanation covers only a portion of the cases. 
If we were purchasing breeding animals for a 
garbage feeding establishment we would regard 
it of considerable advantage to secure them from 
herds long accustomed to that kind of feed. 

Pigs must have dry sleeping quarters or they 
will not thrive. Due to the excessive moisture in 
garbage, wet quarters are a common and disas- 
trous cause of unthriftiness among pigs that sub- 
sist on it. The greater the run allowed the pigs 
the easier it is to keep them dry. When the quar- 
ters are of necessity somewhat crowded, special 



HOG CHOLERA AND MEAT INSPECTION 225 

provisions are necessary or all parts of the floor 
will be clamp. This difficulty can be obviated by 
constructing overlays consisting of floors of 
matched material built on two-by-fours laid flat. 
These are built up around the edges so that in 
effect they are wide shallow boxes which contain 
the litter. They should be located as far as pos- 
sible from the platform where the garbage is fed. 
What we have said in preceding chapters in 
regard to maintaining herds immune to hog chol- 
era applies as well to those that subsist on gar- 
bage. Young garbage-fed pigs are relatively 
somewhat slow in getting started, hence they re- 
quire a little extra care such as we have already 
outlined. In the absence of this care they are in 
more or less danger of falling victims to various 
influences that retard growth, or to ill effects fol- 
lowing simultaneous treatment administered at a 
time when they are not in the best condition to 
withstand it. 

Grarbage Feeding and Sanitary Considerations 

We have already described the cycle which 
enables the practice of garbage feeding to aid in 
perpetuating hog cholera. The ways in which this 
cycle can be assailed remain to be considered. 
Our attacks should include efforts to prevent ship- 
ment from cholera infected herds, gradual revi- 
sion of our meat inspection regulations with a 



226 HOG CHOLEKA 

view to reducing the number of virus containing 
carcasses that are placed on the market, measures 
to license and control establishments where gar- 
bage is fed, and educational activities designed to 
acquaint breeders with the risks they assume 
when they feed even a limited quantity of garbage. 
Measures to prevent shipment from cholera- 
infected herds may take two forms : first, the al- 
ternative — prompt serum treatment — should be 
made available to every breeder, and practicing 
veterinarians will do well to school themselves in 
handling hog cholera on the farm, so that the folly 
of marketing infected hogs will be obvious to the 
breeder ; second, some form of penalty should be 
attached to the practice. It is obviously impos- 
sible to reach all offenders but the more flagrant 
ones could easily be detected, and the effect would 
be wholesome. When a shipment of smne arrives 
at the yards containing a considerable number of 
dead hogs and many others obviously infected 
with cholera, the chances are that most of the 
animals in it will produce carcasses which contain 
the virus. If it could be made compulsory to 
market such carcasses only in the form of safe 
but less valuable cooked products, and if the hogs 
in such a shipment were so tagged and identified 
that the shipper himself had to accept the conse- 
quent loss, there would be fewer cholera infected 



HOG CHOLERA AND MEAT INSPECTION 227 

herds marketed, and a higher price for sound ones 
would prevail. 

Ante-mortem inspection could at least be made 
to incriminate an entire shipment containing hogs 
obviously infected with cholera to the extent of 
requiring a more severe interpretation of lesions 
in individuals contained in it. "While it is true 
that petechia in the kidneys and peripheral hem- 
orrhages in the lymph glands, for instance, may 
be due to causes other than cholera, it is likewise 
true that in shipments such as we have described 
these lesions are, with negligible exceptions, con- 
clusive evidence of the disease. 

License and control of garbage feeding estab- 
lishments have much to recommend them. Sur- 
rounding the average city, under present condi- 
tions, are numerous small herds in which garbage 
is being fed, and in each one lurks the danger of 
an outbreak of hog cholera. If a licensing system 
were in operation, instead of having many un- 
known sources of infection without any control 
whatever, we would have a limited number of 
known sources, in which methods could be so regu- 
lated as to minimize danger due to spread of the 
infection. It would be possible to require immu- 
nization of all hogs fed on garbage — an advantage 
rather than a burden to the individual feeder — 
and it would likewise be possible to govern the 



228 HOG CHOLERA 

location of garbage feeding establishments, and 
to require adequate equipment for their operation. 

Regulations in Canada require that all men who 
plan to feed garbage shall first secure licenses, 
and the plan seems to be working well; princi- 
pally, we believe, because the sources of danger 
are limited in number and known. Cooking the 
garbage is required, but this, in our experience, 
is a measure of doubtful value. There is no doubt 
that a boiling temperature will kill the virus, but 
there is doubt that such a temperature will ac- 
tually be applied to all garbage fed in any estab- 
lishment. We have frequently seen neglect of this 
kind end in disaster. In one instance we were 
called to handle an outbreak of hog cholera at a 
large sanitarium where provision had even been 
made for cooking all garbage under pressure. An 
unguarded interval during which the apparatus 
was temporarily out of order was responsible for 
this outbreak. Immunizing the herd is usually 
far safer than cooking the garbage on which it is 
fed, and it has the additional advantage of pro- 
tecting against all sources of infection. 

Despite the need for various measures to pro- 
tect the swine breeder's herd, the fact remains 
that the measures which he himself can apply will 
be most effective. He can exclude all pork trim- 
mings from the kitchen refuse which he feeds, he 
can discontinue feeding garbage, or he can in co- 



HOG CHOLEKA AND MEAT INSPECTION 229 

operation with his veterinarian keep his herd im- 
munized. Either measure faithfully carried out 
will protect his herd from cholera infection di- 
rectly due to garbage feeding. 



CHAPTER XI 

CONTROL AND ERADICATION OF HOG, CHOLERA 

Control of an infectious disease means that 
rather definite limits have been placed on its 
spread. Eradication, as applied to a particular 
area, implies that all the virus which causes the 
disease has been killed, and that the malady can 
no longer exist unless it is introduced from with- 
out. Naturally, in a country in which an acute 
and fatal infectious disease such as hog cholera 
is widely disseminated control is the first con- 
sideration. But eradication is the distant goal, 
and while our progress toward this goal must at 
times yield to expediency, there must be no per- 
manent or long surrender to methods that con- 
tribute nothing toward the ultimate purpose. 

Long acceptance of losses due to hog cholera 
has given us a fatalistic attitude toward the dis- 
ease. Like the poor, it is always with us and we 
habitually expect and tolerate it as we expect and 
tolerate inclemencies of weather or the infirmi- 
ties of old age. If a foreign infectious SAvine dis- 
ease, equally destructive and equally well under- 
stood, were to appear in this country, even though 

230 



CONTEOL AND ERADICATION OF HOG CHOLERA 231 

it were to gain a firm foothold, those whose inter- 
ests were threatened would demand its eradica- 
tion and the veterinary profession in cooperation 
with many breeders — and in spite of the violent 
opposition of a few — would eradicate it. 

The first prerequisite, then, is a change on the 
part of veterinarians, breeders and the public 
from a passive to an active attitude toward hog 
cholera. In expressing this view we must not be 
understood as declaring our faith in a short and 
intensified campaign against the disease, for the 
methods that finally succeed will involve details 
which must grow out of a continual process of 
trial and adjustment ; but the start must be made, 
the goal must be kept clearly in view, and con- 
stant, active and unyielding pressure must be 
brought to bear on the most obvious practices that 
serve to perpetuate the disease. 

During the last four decades hog cholera has 
caused in this country annual losses ranging be- 
tween $13,000,000 and $200,000,000, killing annu- 
ally an average of 66 out of every 1,000 hogs. 
About once in each decade the disease becomes 
greatly intensified and in 1887, 1897 and 1914, 
respectively, the number of hogs killed by it rose 
above 10 per cent of the country's entire swine 
population. These are staggering losses, and 
when one reflects that they will continue indefi- 
nitely unless intelligent, organized efforts are 



232 " HOG CHOLERA 

made to check them the advantages of such efforts 
become self-evident. 

It is not impossible to eradicate hog cholera. 
The task presents no such diflficulties as are en- 
countered in the eradication of bovine tuberculo- 
sis, for instance. Hog cholera does not exist long 
unknown to the owner of the herd it infects ; indi- 
viduals apparently well do not regularly live year 
after year disseminating the virus ; deaths due to 
it are rapid and certain and the resulting losses 
are obvious; it is a foe that strikes in the open. 
The disease can be stamped out quickly in any 
herd, and there is an immunizing agent so etfec- 
tive that prompt reporting is the breeder ^s surest 
way to avoid loss. When we reflect on the sig- 
nificance of these facts we may well be led to 
wonder why the disease does not disappear. The 
truth is that it does tend to do so, for undoubtedly 
there are to-day many counties free from the dis- 
ease that have suifered severely from it in past 
years, and that will suffer again when the virus 
once more is introduced from without. 

When once the virus finds its way into a locality 
the methods by which it may spread from herd to 
herd are innumerable but it is time that we direct 
our attention to the sources of the original infec- 
tions. We dissipate our energies in trying to con- 
trol outbreaks of huge proportions instead of 
concentrating them on the prevention of primary 



CONTROL AND ERADICATION OF HOG CHOLERA 233 

infections. The three most important methods by 
which hog cholera travels from locality to locality 
are: 

1. Marketing from infected herds. The hogs 
thus shipped are a menace to others as they are 
taken to market, they keep stock cars and stock- 
yards constantly infected, they are sometimes sold 
from the yards as feeders, and their carcasses are 
regularly placed on the market in large numbers 
where they serve to infect many new localities 
through the medium of garbage feeding. 

2. The transportation from public stock- 
yards of susceptible feeder hogs, and those 
which receive simultaneous treatment imme- 
diately prior to shipping. Wlien susceptible 
feeders are placed in public stockyards they often 
become infected, and though they leave the yards 
apparently in good health they soon develop 
cholera and the farms which receive them become 
new centers of infection. Feeder hogs that receive 
simultaneous treatment and which are at once 
shipped to distant points, frequently ^ 'break" as 
.a result, and thus introduce hog cholera into new 
territory. 

3. Wide and indiscriminate use of hog cholera 
virus in immunizing, especially by untrained 
men. '^ Vaccination cho]er.a" is still too common 
in farm herds, despite the fact that experienced 
men know how to avoid most of it. 



234 HOG CHOLEEA 

These three practices have essentially the same 
relation to hog cholera eradication that the feed- 
ing of uncooked creamery products has to the 
eradication of bovine tuberculosis. They furnish 
obvious and wide-open routes for dissemination 
of the virus. Are they really necessary evils! 
Are there no possible ways to avoid them? Let 
us examine the three practices more in detail. 

Marketing from infected herds. We have al- 
ready shown that marketing from infected herds 
is a common practice, that it serves to spread hog 
cholera virus as the animals are driven to market 
and when trimmings from their carcasses later 
find their way into garbage that is fed to suscep- 
tible hogs. We have also drawn attention to the 
fact that feeders selected from these herds and 
shipped to distant points cause many new out- 
breaks of hog cholera. For our present purpose 
it remains to review briefly means by which this 
endless chain of infection can be severed. 

The first object should be to keep cholera in- 
fected herds at home. Good local veterinary serv- 
ice will do much in this direction for it is the ill- 
advised breeder who ships his infected hogs to 
market. On the part of the meat inspection serv- 
ice, rigid interpretations of lesions in all indi- 
viduals that come from lots obviously infected 
with hog cholera at the time they reach the yards 



♦ 



CONTROL AND ERADICATION OF HOG CHOLERA 235 

will serve to discourage shipping from infected 
herds, provided a tagging system is adopted which 
will place the losses due to condemnations where 
they belong — on the man who ships the hogs. 

The second object should be to prevent the sale 
of carcasses of infected hogs that reach market 
despite efforts to keep them away. In other 
words, carcasses that obviously are carriers of 
hog cholera virus should not be sold except in the 
form of cooked products, for hog cholera will be 
with us as long as the practice continues. We 
have already mentioned the present deficiency of 
the federal meat inspection regulations as they 
apply to this particular point. Whether this de- 
ficiency is due to lack of authority or to failure to 
use authority already granted, the etfect is the 
same — many carcasses that show lesions usually 
considered characteristic of hog cholera are still 
allowed to pass inspection. 

It is deceptive to assert, as the regulations do, 
that these lesions are sometimes due to causes 
other than hog cholera. Granting, as we freely 
do, that this is true we still maintain that it is 
exceptional to such an extent that it should re- 
ceive scant consideration in the judgment of car- 
casses that come from lots which contain hogs 
suffering with cholera w^hen they reach the yards. 
Hogs that come from infected herds and that show 



236 HOG CHOLERA 

even slight lesions suggestive of cholera mil yield 
carcasses that contain virus, almost without ex- 
ception. 

The third object sought should be that of neu- 
tralizing the effects of virus-carrying carcasses 
that pass inspection. To this end it should be 
made known among swine raisers that danger al- 
ways lurks in the practice of feeding even small 
quantities of garbage that contain pork trim- 
mings. A system of licensing garbage-feeding 
such as the one that now exists in Canada, is also 
Avorthy of consideration. 

Transportation and sale of susceptible feeder 
hogs and those tvhich receive simidtaneous treat- 
ment just before shipping. Most public stock- 
yards are contaminated with hog cholera virus, 
and eventualh^ it should be so ordered that when 
susceptible hogs enter, it shall be for immediate 
slaughter only, and the gates shall close behind 
them forever. Previously we have drawn atten- 
tion to the fact that ^' serum breaks" are fre- 
quently a result of giving hogs simultaneous treat- 
ment and shipping them immediately afterward. 

Though this practice is probably the lesser evil 
as compared to shipping susceptible hogs from the 
yards without immunization, the fact remains that 
it is still a potent factor in the dissemination of 
hog cholera virus. Follow-up treatment as a sub- 
stitute for simultaneous treatment given immedi- 



CONTROL AND ERADICATION OF HOG CHOLERA 237 

ately before shipping, will do much to minimize 
this danger, but the ideal will be reached only 
when feeder hogs are permanently immune to hog 
cholera before they are shipped long distances. 

It will take time to provide for an adequate 
supply of immune feeders so that shipping suscep- 
tible and recently-immunized hogs from public 
stockyards will not be necessary, but there are 
hopeful indications that this will be brought about. 
Men experienced in the feed-yard even now are 
eagerly seeking means of avoiding the heavy 
financial losses associated with ^Vaccination 
cholera'' immediately following simultaneous 
treatment and shipping. Among such men there 
is an active demand for immune feeder shoats, 
and efforts are being made, though as yet on a 
limited scale, to supply this demand. The prac- 
tice of assembling and immunizing feeders, and 
shipping them only after the resulting reaction 
is over is already being adopted by some serum 
companies. This is a step in the right direction, 
and our belief is that a promising field is open to 
others who will make a business of supplying the 
trade with carefully selected cholera - immune 
feeder shoats. When the supply of these animals 
is equal to the demand the practice of shipping 
susceptible and recently-immunized feeders from 
public stock^^ards will cease. 

Indiscriminate use of hog cholera virus in im- 



238 HOG CHOLERA 

muyiizing. When the effectiveness of serum-virus 
immunization was first demonstrated the demand 
for these products far exceeded the supply, and 
hasty preparations were made to produce them in 
enormous quantities. Enthusiasm for immuniza- 
tion ran high, and it was looked on as the final 
solution of the hog cholera problem. Men with- 
out previous experience with disease and with 
no fundamental knowledge of the processes that 
produce immunity were drafted into service to 
produce and use products potentially capable of 
doing great harm. It was the accepted belief that 
all hogs should be immunized, that the process of 
immunization was a simple one requiring only a 
low grade of mechanical skill, that serum and 
virus could be administered without a suggestion 
of danger, and that the hogs receiving them were 
from the moment the doses were administered 
permanently immune to hog cholera. It is little 
wonder that impotent serum was sent out, that 
potent serum often fell into unskilled hands, and 
that some of the laboratories that featured *^ virus 
q. s. with all serum orders'' sometimes sent out 
quantities that were just a little more than suffi- 
cient. 

The Bureau of Animal Industry laboratory in- 
spection service ^dth the aid of many far-sighted 
serum companies has done much to correct these 
initial evils. The sale of impotent serum for use 



CONTROL AND ERADICATION OF HOG CHOLERA 239 

with virus was much more readily prevented than 
were the disasters growing out of the use of good 
serum by untrained or indifferent men, and to- 
day it is to the latter abuse that most outbreaks 
of hog cholera which originate from laboratory 
virus must be attributed. 

The task of reducing '^vaccination cholera'* to 
a minimum must be referred to a trained and 
awakened veterinary profession. There is an in- 
sistent demand that vaccination of hogs shall be 
placed in the hands of laymen, a policy which, if 
adopted generally, will be disastrous to the swine 
industry. Yet this demand will be heard — and 
heeded — as long as there is territory in which 
there are not qualified veterinarians to do the 
work. 

Reducing the problem of hog cholera control to 
its simplest terms it may be said that in the indi- 
vidual animal the disease soon terminates, for the 
virus will destroy or immunize its host in a few 
weeks. Likewise in the herd the same principle 
applies, but if we expand our unit to include 
county, state or nation the difficulties that present 
themselves multiply accordingly. The limiting 
factors in the control of the disease are lack of 
thoroughly trained men, lack of understanding on 
the part of the public, and the expense involved. 

The federal Bureau of Animal Industry has 



240 HOG CHOLEKA 

demonstrated that the disease can be kept down in 
individual counties, but tlie expense involved was 
so great as to forbid use of the plan on a large 
scale. Area work in the eradication of hog chol- 
era is, we believe, wrong in its conception as long 
as the virus continually invades the selected terri- 
tory from without through the three channels that 
have just been indicated. 

No successful standardized plan for the control 
of hog cholera has yet appeared. Killing infected 
and exposed animals and indemnifying the owners 
has been tried in England and Canada but results 
have not been such as to recommend wide applica- 
tion of the plan. Immunizing all hogs against 
cholera was once enthusiastically recommended, 
but we doubt if there can be found to-day an ex- 
perienced man who considers this method feasible. 
It would involve the principle of forcing owners 
to vaccinate, the expense would be prohibitive, 
and the trained men necessary to carry it out do 
not exist. 

In our appraisal of the cooperative forces 
which can be brought to bear immediately in hog 
cholera eradication we must include the swine 
breeder, the practicing veterinarian, the official 
veterinarian and the serum producer. 

The breeder should be acquainted with the 
methods by which hog cholera is spread so as to 
be able to protect his herd against extraneous 



CONTROL AND ERADICATION OF HOG CHOLERA 241 

infection. He should, with the advice of his 
veterinarian determine whether his herd is to be 
maintained immmie to hog cholera, or whether it 
is to remain susceptible and be kept under obser- 
vation. In case the former plan is adopted the 
practice of immunizing should not be allowed to 
lag, and in case the latter seems advisable he 
should report promptly any infectious disease 
that appears. 

The practicing veterinarian's part consists in 
snuffing out the outbreaks as fast as they appear, 
in aiding owners to clean up their herds so that 
they will not serve to infect others in the vicinity, 
in doing the vaccinating incident to maintaining 
immune herds, and in advising his clients relative 
to methods by which their herds can best be pro- 
tected. Only when the need for police power ap- 
pears does the province of the practitioner ter- 
minate and that of the official veterinarian begin. 

The official veterinarian's primary duty is to 
bring pressure to bear on the three principal 
practices that serve to spread hog cholera from 
locality to locality. By placing restrictions on the 
sale of hogs from infected herds and from public 
stockyards ; by a far more severe interpretation of 
hog-cholera-like lesions in the administration of 
meat inspection regulations ; by restricting the use 
of virus so that only trained men may handle 
it; and by continued supervision of commercial 



242 HOG CHOLEKA 

serum laboratories the official veterinarian can 
play an indispensable part in the fight against hog 
cholera. 

The serum producer's part is to supply suffi- 
cient potent serum to immunize all hogs that ac- 
tually require immunization. Despite notable ex- 
ceptions it must be said that on the whole the part 
has been played well, and when breeders, prac- 
ticing veterinarians and official veterinarians, as 
classes, meet their obligations as well as the serum 
producer is meeting his, there will be far less hog 
cholera in the country. 

Volumes could be written on the eradication of 
hog cholera if we were to follow the various rami- 
fications into which details of the problem lead us. 
There are the questions of uniform regulations 
for interstate shipment of swine ; of separate reg- 
ulations for crated swine; of rules governing the 
exhibition of hogs at fairs ; and of funds to admin- 
ister laws and regulations that are already pro- 
vided. These and many other supplementary 
problems appear but consideration of them here 
w^ould only cloud the more important issues. 

The points we emphasize in closing are that at 
the present time the obstacles presented in the 
eradication of hog cholera rest not so much in 
lack of machinery to do the work as in the manner 
in which the existing machinery functions; that 
three well-known wide-open routes for the inter- 



CONTROL AND ERADICATION OF HOG CHOLERA 243 

sectional spread of hog cholera virus still exist 
and that thej^ must be closed as the first step to- 
ward substantial progress in eradicating the dis- 
ease. Only when this is accomplished can we 
correctly appraise the lesser task that will yet 
remain. At present the country's attitude toward 
hog cholera eradication may be likened to that of 
a farmer who each year sows weed seeds with his 
grain, and then labors diligently to eradicate the 
weeds that spring up. Let us stop sowing the seed. 

References 

The following references have been selected from the 
numerous publications on hog cholera because most of 
them are available to the American veterinarian, and 
because, as a group, they cover the subject in a fairly 
complete and satisfactory manner. No attempt has been 
made to include a complete bibliography. 

Birch, R. R., **Hog Cholera and Its Prevention," Cor- 
nell Veterinarian, Hog Cholera Number, May, 1916. 

Birch, R. R., *' Garbage Feeding and the Care of Gar- 
bage-fed Swine," Cornell Veterinarian, January, 
1918, p. 26. 

Birch, R. R., "Hog Cholera Transmission Through In- 
fected Pork," Journal of the Am. Vet. Med. Assn., 
June, 1917, p. 303. 

Birch, R. R., "Researches in Regard to Immunizing 
Young Pigs, ' ' Report of the New York State Veter- 
inary College at Cornell University, 1918-1919, 
p. 73. 

Cahill, E. a., "Hog Cholera Control in the East," 
Journal of the Am. Vet. Med. Assn., January, 1919, 
p. 314. 



244 HOG CHOLERA 

Cahill, E. a., ''Relative Potency of Tail-bled and 
Carotid-bled Anti-hog-cholera Serum," Journal of 
the Am. Vet. Med. Assn., November, 1919, p. 177. 

CoNNOWAY, J. W., ' ' Hog Cholera and Immature Corn, ' ' 
Bulletin No. 74, University of Missouri College of 
Agriculture. 

De Schweinitz and Dorset, "A Form of Hog Cholera 
not Caused by the Hog Cholera Bacillus," Circular 
No. 41, U. S. Bureau of Animal Industry. 

DiMOCK, W. W., "Differential Diagnosis of Diseases of 
the Pig," Journal of the Am. Vet. Med. Assn., Janu- 
ary, 1919, p. 321. 

Dorset, Bolton, McBryde, "The Etiology of Hog 
Cholera," Bulletin No. 72, U.S.Bureau of Animal 
Industry. 

Dorset, McBryde, Niles, "Further Experiments Con- 
cerning the Production of Immunity from Hog 
Cholera," Bulletin No. 102, U. S. Bureau of Animal 
Industry. 

Dorset, M., and Houck, U. G., "Hog Cholera," Farm- 
ers' Bulletin No. 834, U. S. Department of Agricul- 
ture. 

Dorset, M., McBryde, C. N., Niles, W. B., Rietz, J. H., 
"Studies on H3q3erimmunization against Hog Chol- 
era," Journal of the Am. Vet. Med. Assn., June, 
1919, p. 259. 

Eichhorn, a., "Present Status of Hog Cholera Con- 
trol, ' ' J&urnal of the Am. Vet. Med. Assn., October, 
1919, p. 51. 

Prink, W. E., "The Control of Hog Cholera," Cornell 
Veterinarian, October, 1920, p. 244. 

HosKiNS, H. Preston, "Notes on the Occurrence of 
Petechial Hemorrhages in the Larynx and Kidneys 
in Hog Cholera," Journal of the Am. Vet. Med. 
Assn., July, 1916, p. 478. 

Hoskins, H. Preston, "Observations on 2800 Pigs In- 
oculated with Hog Cholera Virus," Journal of ihe 
Am. Vet. Med. As^n., September, 1915, p. 817. 



CONTROL AND ERADICATION OF HOG CHOLERA 245 

HoucK, U. G., ''Progress in Hog Cholera Control," 
Journal of the Am. Vet. Med. Assn., January, 1920, 
p. 359. 

Kernkamp, H. C. H., ''The Longevity of the Virus of 
Hog Cholera," Cornell Veterinarian, January, 1920, 
p. 1. 

Kerni^amp, H. C. H., "Results of Experiments to Note 
the Effects of Freezing on Anti-hog-Cholera Se- 
rum," Cornell Veterinarian, January, 1918, p. 7. 

King, W. E., and Hoffman, G. L., "Spiroehifta Suis : 
Its Significance as a Pathogenic Organism," Journal 
of Infectious Diseases, Vol. 13, p. 463. 

King, W. E., Baeslach, F. W., Hoffman, G. L., "Stud- 
ies on the Virus of Hog Cholera, ' ' Am. Vet. Review, 
Vol. 44, p. 555. 

Kinsley, A. T., Swine Practice (Am. Veterinary Pub- 
lishing Co., Chicago). 

Lynch, Chas. F., Diseases of Swine (AV. B. Saunders 
Co., Philadelphia). 

JMoore, V. A., DiMOCK, W. W., Haring, C. M., Gilli- 
LAND, S. H., Kinsley, A. T., "Report of the Com- 
mittee on Diseases," Journal of the Am. Vet. Med. 
Assn., November, 1915, p. 207. 

Meyer, "The Filterable Viruses," Am. Vet. Review, 
Vol. 46, No. 2, p. 132. 

NiLEs, W. B., "Field Tests with Serum for the Preven- 
tion of Hog Cholera," Report of the U. S. Bureau 
of Animal Industry, 1908. 

NiLES, W. B., RiETZ, J. H., "Immunity of Young Pigs," 
Journal or the Am. Vet. Med. Assn., May, 1920, 
p. 176. 

Palmer, C. B., "The Hog in Relation to Municipal Gar- 
bage," Journal of the Am. Vet. Med. Assn., 1918, 
p. 227. 

Pickens, E. M., Welsh, M. F., Polema, L. J., "The 
Susceptibility of Young Pigs to Cholera," Journal 
of the Am. Vet. Med. Assn., October, 1921, p. 22. 

Records, Edward, ' ' Purification and Concentration of 
Hog Cholera Serum," Journal of the Am,. Vet. 
Med. Assn., December, 1919, p. 291. 



246 HOG CHOLEKA 

Stange, C. H., ''Hog Cholera Control," Journal of the 
Am. Vet Med. Assn., November, 1915, p. 156. 

Torrance, Frederick, "Garbage Feeding in Relation to 
the Control of Hog Cholera," Journal of the Am. 
Vet. Med. Assn., October, 1921, p. 22. 



APPENDIX 

B. A. I. Order 265. Issued September 12, 1919. 

UNITED STATES DEPARTMENT OF 
AGRICULTURE 

Bureau of Animal Industry 
John R. Mohler, Chief of Bureau 

Regulations Governing the Preparation, Sale, Barter, 
Exchange, Shipment, and Importation of Viruses, 
Serums, Toxins, and Analogous Products Intended for 
Use in the Treatment of Domestic Animals. 

Effective on and after September 1, 1919 
CONTENTS 

Page. 

Regulation 1. Definitions 248 

Regulation 2. Licenses and inspections 251 

Regulation 3. Permits 254 

Regulation 4. Suspension or revocation of licenses 

and permits 256 

Regulation 5. Notice to licensees and permittees. . 257 

Regulation 6. Assignment of bureau employees. . . 257 

Regulation 7. Facilities for inspection 258 

Regulation 8. Sanitation 258 

Regulation 9. Sterilization 261 

Regulation 10. Storage 262 

Regulation 11. Records 262 

Regulation 12. Labels 263 

Regulation 13. Collecting samples 265 

Regulation 14. Testing 266 

Regulation 15. Retesting 266 

247 



248 HOG CHOLEKA 

Page. 

Regulation 16. Reports 266 

Regulation 17. Animals 267 

Regulation 18. Hog-cholera virus 274 

Regulation 19. Anti-hog-cholera serum 282 

Regulation 20. Bacterins, vaccines, toxins, etc. . . . 295 
Regulation 21. Admission of viruses, serums, tox- 
ins, and analogous products 296 

The virus-serum-toxin law 296 

U. S. Department of Agriculture, 

Office of the Secretary, 
Washingto7i, D. C, August 1, 1919. 

Under authority of the act of Congress approved 
March 4, 1913, entitled "An act making appropriations 
for the Department of Agriculture for the fiscal year 
ending June 30, 1914" (37 Stat., 832), the following 
regulations are hereby issued for the purpose of en- 
forcing the provisions of said act governing the prepara- 
tion, sale, barter, exchange, shipment, and importation 
of viruses, serums, toxins, and analogous products in- 
tended for use in the treatment of domestic animals. 
These regulations, which for the purpose of identification 
are designated as B. A. I. Order 265, shall become and 
be effective on and after September 1, 1919, except that 
stocks of approved labels on hand may be used until 
December 31, 1920. 

D. F. Houston, 
Secretary of Agriculture. 

EEGULATION 1. — DEFINITIONS 

Section 1. Paragraph 1. For the purpose of these 
regulations the following Avords, phrases, names, and 
terms shall be construed respectively to mean : 

Paragraph 2. The virus-serum-toxin act of 1913 : *' An 
act making appropriations for the Department of Agri- 



APPENDIX 249 

culture for the fiscal year ending June 30, 1914," ap- 
proved March 4, 1913 (37 Stat., 832). 

Paragraph 3. Viruses, serums, toxins, and analogous 
products or veterinary biologies: All viruses, serums, 
toxins, and analogous products, such as antitoxins, vac- 
cines, tuberculins, malleins, microorganisms, killed micro- 
organisms, and products of microorganisms which are 
intended for use in the treatment of domestic ani- 
mals. 

Paragraph 4. The department : The United States De- 
partment of Agriculture. 

Paragraph 5. The bureau : The Bureau of Animal In- 
dustry of the IJnited States Department of Agriculture. 

Paragraph 6. Bureau employee : Any officer, agent, 
or other individual employed in the Bureau of Animal 
Industry, who is authorized by the chief of the bureau to 
do any work or perform any duty in connection with the 
execution of the provisions of the virus-serum-toxin act 
of 1913. 

Paragraph 7. Veterinary inspector: A veterinary in- 
spector of the Bureau of Animal Industry. 

Paragraph 8. Licensed establishment : Any establish- 
ment owned or operated by a person, firm, or corporation 
holding an unexpired, unsuspended, and unrevoked li- 
cense issued by the Secretary of Agriculture for the 
preparation of any virus, serum, toxin, or analogous 
product. 

Paragraph 9. Official station: One or more licensed 
establishments included under a single supervision. 

Paragraph 10. Inspector in charge : An inspector as- 
signed to supervise and perform official work at an offi- 
cial station and who reports directly to the chief of the 
bureau. 

Paragraph 11. Person: Natural persons, individuals, 
firms, partnerships, corporations, companies, societies, 
and associations and every agent, officer, or employee 



250 HOG CHOLERA 

thereof. This term shall import both the plural and 
the singular, as the case may be. 

Paragraph 12. Hog-cholera virus: The clear serum, 
plasma, or defibrinated blood, derived from hogs sick of 
hog cholera and free from other communicable disease 
or diseases. 

Paragraph 13. Hyperimmunizing virus : Hog-cholera 
virus prepared for hyperimmunizing hogs which are im- 
mune to the disease hog cholera. 

Paragraph 14. Simultaneous virus : Hog-cholera virus 
prepared for inoculating hogs which are to be injected 
simultaneously with anti-hog-cholera serum for the im- 
munization of those animals against the disease hog 
cholera. 

Paragraph 15. Anti-hog-cholera serum : The clear 
serum, plasma, or defibrinated blood, or derivatives there- 
of, containing the protective principles derived from im- 
mune hogs which have been hyper-immunized by an in- 
travenous injection of at least 5 cubic centimeters, per 
pound body weight, of the virus of hog cholera. 

Paragraph 16. Immediate or true container: The 
unit, bottle, vial, ampule, tube, or other receptacle or con- 
tainer in which any virus, serum, toxin, or analogous 
product is customarily sold or distributed. 

Paragraph 17. Serial number : The number given each 
batch of virus, serum, toxin, or analogous product to 
identify the said virus, serum, toxin, or analogous prod- 
uct with the records of preparation thereof. 

Paragraph 18. Return date: The date placed upon 
trade labels affixed to or used in connection with imme- 
diate or true containers of viruses, serums, toxins, and 
analogous products by producers to indicate the limit 
of time during which the said products may be expected 
to retain their full strength or potency. 

Paragraph 19. U. S. Released: That veterinary bi- 
ologies so marked have been prepared and tested in ac- 



APPENDIX 251 

cordance with the provisions of these regulations and 
that when thus prepared, tested, and marked, they were 
not worthless, contaminated, dangerous, or harmful. 

REGULATION 2. — LICENSES AND INSPECTIONS 

Section 1. Every establishment in the United States 
at which any virus, serum, toxin, or analogous product 
is prepared for sale, barter, or exchange in the District 
of Columbia or in any Territory of or place under the 
jurisdiction of the United States, or for shipment or de- 
livery for shipment from any State or Territory or the 
District of Columbia to any other State or Territory or 
the District of Columbia, shall hold an unexpired, unsus- 
pended, and unrevoked license, issued by the Secretary 
of Agriculture, and shall have inspection under these 
regulations. 

Section 2. All viruses, serums, toxins, and analogous 
products produced at licensed establishments shall be 
prepared, handled, stored, marked, received for trans- 
portation, and transported as required by these regula- 
tions. 

Section 3. Paragraph 1. The proprietor or operator 
of each establishment of the kind specified in section 1 
of this regulation shall make application in writing to 
the Secretary of Agriculture for a license. When one 
proprietor conducts more than one establishment, a sep- 
arate application- shall be made for a license for each 
establishment. Blank forms of application will be fur- 
nished upon request addressed to the Bureau of Animal 
Industry, Washington, D. C. 

Paragraph 2. Triplicate copies of plans, properly 
drawn to scale, and of specifications, including plumbing 
and drainage of establishments, together with triplicate 
copies of all labels and advertising matter to be used 
in connection with or relating to all viruses, serums, 
toxins, and analogous products prepared therein, shall 
accompany the application for a license, unless these 



252 HOG CHOLEKA 

plans, specifications, labels, and advertising matter have 
already been approved in writing by the bureau. 

Paragraph 3. In case of change in ownership or loca- 
tion while an application is pending, or after a license 
has been issued, a new application shall be made. 

Section 4. Paragraph 1. A license will not be issued 
unless the condition of the establishment and the methods 
of preparation are such as reasonably to insure that the 
product will accomplish the object for which it is in- 
tended and that such product is not worthless, contamin- 
ated, dangerous, or harmful. 

Paragraph 2. A license will not be issued unless and 
until the establishment is prepared to operate under 
the direct supervision of a competent person trained in 
bacteriological technique and in the preparation of 
viruses, serums, toxins, or analogous products named in 
the application. 

Paragraph 3. A license will not be issued for the 
preparation of any virus, serum, toxin, or analogous 
product if advertised so as to mislead or deceive the pur- 
chaser, or if the package or container in which the same 
is intended to be sold, bartered, exchanged, or shipped 
bears or contains any statement, design, or device which 
is false or misleading in any particular. 

Section 5. Paragraph 1. A license will be issued 
only after inspection of the establishment by a bureau 
employee has shown that the condition and equipment 
of the establishment and the methods of preparing, han- 
dling, and storing are in conformity with these regula- 
tions. 

Paragraph 2. Licenses shall be numbered and shall be 
in the following form : 

United States Veterinary License No 



Washington, D. C, 19 . . 

This is to certify that, pursuant to the terms of the act 
of Congress approved March 4, 1913 (37 Stat., 832), 



APPENDIX 253 

governing the preparation, sale, barter, exchange, ship- 
ment, and importation of virnses, serums, toxins, and 
analogous products intended for use in the treatment of 

domestic animals, is 

hereby licensed to maintain at Street, 

city or town of , State of , 

an establishment for the preparation of 

during the calendar year 19. . .. 

This license is subject to suspension or revocation if 
the licensee violates or fails to comply with any provision 
of said act approved March 4, 1913, or of the regulations 
made thereunder. 



Secretary of Agriculture. 
Countersigned : 



Chief, Bureau of Animal Industry. 

Two or more licenses may bear the same number when 
they are issued to firms under the same ownership or 
control, provided a serial letter is added when necessary, 
to identify each license. 

Paragraph 3. Each license shall teminate at the end 
of the calendar year for which it is issued. 

Section 6. Paragraph 1. No viruses, serums, toxins, 
or analogous products shall be prepared in whole or in 
part in a licensed establishment by any other licensed 
establishment unless authorized in advance by the chief 
of bureau. 

Paragraph 2. Each licensed establishment shall be 
separate and distinct from any unlicensed establishment 
in which any virus, serum, toxin, or analogous product 
is prepared or handled. 

Paragraph 3. When a license is issued the bureau 
shall inform the proprietor or operator of the establish- 
ment of the requirements of these regulations. If the 
establishment at the time the license is issued contains 
any viruses, serums, toxins, or analogous products, which 



254 HOG CHOLERA 

have not theretofore been prepared, and of which the 
containers have not been theretofore marked, in com- 
pliance with these regulations, the identity of the same 
shall be maintained and they shall not be shipped or 
delivered for shipment from any State or Territory or 
the District of Columbia to any other State or Terri- 
tory or the District of Columbia, or otherwise dealt with 
as products prepared under these regulations. The es- 
tablishment shall adopt and enforce all necessary meas- 
ures, and shall comply with all such directions as the 
chief of bureau may prescribe for carrying out the pur- 
poses of this paragraph. 

REGULATION 3. — ^PERMITS 

Section 1. Each importer of viruses, serums, toxins, 
or analogous products shall hold an unexpired, unsus- 
pended, and unrevoked permit issued by the Secretary 
of Agriculture. 

Section 2. Paragraph 1. Each importer of viruses, 
serums, toxins, and analogous products shall make appli- 
cation in writing to the Secretary of Agriculture for a 
permit. The application shall specify the port or ports 
of entry at which the imported articles will be cleared 
through the customs. Blank forms of application will 
be furnished upon request addressed to the Bureau of 
Animal Industry, Washington, D. C. 

Paragraph 2. Each application for a permit shall be 
accompanied by the affidavit of the actual manufacturer 
produced before an American consular officer, giving 
the city or town where the viruses, serums, toxins, or 
analogous products mentioned therein are prepared, and 
stating that said products are not worthless, contami- 
nated, dangerous, or harmful, whether the products were 
derived from animals, and if so derived, that such ani- 
mals had not been exposed to any infectious or conta- 
gious disease, except as may have been essential in the 



APPENDIX 255 

preparation of the products and as specified in the affi- 
davit. 

Paragraph 3. Each application for a permit shall be 
accompanied by the written consent of the actual manu- 
facturer that properly accredited employees of the de- 
partment shall have the privilege of inspecting, without 
previous notification, all parts of the establishment at 
which such viruses, serums, toxins, or analogous prod- 
ucts are prepared, and all processes of and all records 
kept relative to the preparation of such products at 
such times as may be demanded by the aforesaid em- 
ployees. 

Paragraph 4. Each application for permit shall be 
accompanied by triplicate copies of all labels and adver- 
tising matter. 

Section 3. A permit will not be issued for the impor- 
tation of any viruses, serums, toxins, or analogous prod- 
ucts if advertised so as to mislead or deceive the pur- 
chaser, or if the package or container in which the same 
is intended to be sold, bartered, exchanged, shipped, or 
imported, bears or contains any statement, design, or 
device which is false or misleading in any particular. 

Section 4. Paragraph 1. Permits shall be numbered 
and shall be in the following form : 

United States Veterinary Permit No 

Washington, D. C, , 19 . . . 

This is to certify that, pursuant to the terms of the act 
of Congress approved March 4, 1913 (37 Stat., 832), 
governing the preparation, sale, barter, exchange, ship- 
ment, and importation of viruses, serums, toxins, and 
analogous products intended for use in the treatment of 

domestic animals, , of 

, State of , is hereby 

authorized, so far as the jurisdiction of the Department 

of Agriculture is concerned, to import 

manufactured by , of 

, into the United States through the port 



256 HOG CHOLERA 

of during the calendar year 

19.... 

This permit is subject to suspension or revocation if 
the permittee violates or fails to comply with the pro- 
visions of the said act approved March 4, 1913, or of the 
regulations made thereunder. 



Secretary of Agriculture. 
Countersigned : 



Chief, Bureau of Animal Industry. 

Paragraph 2. Each permit shall terminate at the end 
of the calendar year for which it is issued. 

REGULATION 4. — SUSPENSION OR REVOCATION OF LICENSES 

AND PERMITS 

Section 1. Licenses or permits may be suspended or 
revoked after opportunity for hearing has been accorded 
the licensee or permittee if it appears — 

(1) That the construction of the establishment in 
which the viruses, serums, toxins, or analogous products 
are prepared is defective, or that the establishment is 
improperl}^ conducted ; 

(2) That the methods of preparation are faulty, or 
that the said products contain impurities or lack po- 
tency ; 

(3) That the products are labeled so as to mislead or 
deceive the purchaser in any particular; 

(4) That the license or permit is used to facilitate or 
effect the preparation, sale, barter, exchange, shipment, 
or importation of any worthless, contaminated, danger- 
ous, or harmful viruses, serums, toxins, or analogous 
products; or 

(5) That the licensee or permittee has violated or 
failed to comply wdtli any provision of the virus-serum- 
toxin act of 1913, or of the rules and regulations made 
thereunder. 



APPENDIX 257 

Section 2. All hearings shall be private and at times 
and places designated by the Secretary of Agriculture. 
The parties interested may appear in person or by at- 
torney, and may submit oral or written evidence on the 
questions involved. Upon request and by paying the 
cost, the person involved will be furnished with a copy 
of the transcript of the hearing. 

REGULATION 5. — NOTICE TO LICENSEES AND PERMITTEES 

Section 1. If at any time it appears that the prepa- 
ration, sale, barter, exchange, shipment, or importation 
of any virus, serum, toxin, or analogous product by any 
person holding a license or permit may be dangerous in 
the treatment of domestic animals, the Secretary of 
Agriculture will so notify the licensee or permittee, and 
unless and until the Secretary of Agriculture shall oth- 
erwise direct, no person, so notified, shall thereafter pre- 
pare, sell, barter, or exchange, nor shall thereafter ship, 
offer for shipment, or import any of such product. 

regulation 6. ASSIGNMENT OF BUREAU EMPLOYEES 

Section 1. Any bureau employee, as defined in these 
regulations, shall be permitted to enter any establish- 
ment licensed under these regulations at any hour dur- 
ing the daytime or nighttime ; and such bureau employee 
shall be permitted to inspect without previous notifica- 
tion the entire premises of the establishment, including 
all buildings, compartments, and other places, and all 
equipment such as chemicals, instruments, apparatus, 
and the like, as well as the methods used in the manu- 
facture of, and all records maintained relative to viruses, 
serums, toxins, or analogous products. 

Section 2. Each bureau employee, as defined in these 
regulations, will be furnished with a numbered official 
badge, which he shall not allow to leave his possession. 
This badge shall be sufficient identification to entitle him 



258 HOG CHOLERA 

to admittance at all regular entrances and to all parts of 
the licensed establishment and premises and to any place 
at any time for the purpose of making an inspection 
pursuant to section 1 of this regulation. 

REGULATION 7. FACILITIES FOR INSPECTION 

Section 1. When required by the chief of bureau or 
the inspector in charge, the following facilities, and such 
others as may be essential to efficient conduct of inspec- 
tion, shall be furnished by each licensed establishment: 

{a) Satisfactory pens, equipment, and assistance for 
conducting tests required in accordance with these regu- 
lations. 

(&) Suitable rooms, compartments, or receptacles in 
such number and places as may be necessary for holding 
any viruses, serums, toxins, or analogous products for 
treatment or testing required in accordance with these 
regulations. Such rooms, compartments, or receptacles 
shall be equipped for secure locking and shall be held 
under locks furnished by the department, and the keys 
of such locks shall not leave the custody of bureau em- 
ployees. 

REGULATION 8. — SANITATION 

Section 1. Paragraph 1. Triplicate copies of plans 
properly drawn to scale, and of specifications, including 
plumbing and drainage, for remodeling plants of licensed 
establishments and for new structures, should be sub- 
mitted to the chief of bureau in advance of construction. 

Paragraph 2. Stables or other premises for animals 
used in the production or testing of viruses, serums, tox- 
in^, or analogous products shall be properly ventilated 
and lighted, appropriately drained and guttered, and 
kept in good sanitary condition. 

Paragraph 3. Animals infected with or exposed to 
any infectious, contagious, or communicable disease shall 
be properly segregated. 



APPENDIX 259 

Paragraph 4. Licensed establishments shall be so lo- 
cated as to avoid the spread of disease, and suitable 
arrangements shall be made for the disposal of all 
refuse. 

Paragraph 5. Direct communication to licensed es- 
tablishments shall not be maintained from public stock- 
yards, abattoir pens, or other places in which animals 
are received or held for any purpose. 

Paragraph 6. All viruses, serums, toxins, and analo- 
gous products shall be prepared, handled, and distrib- 
uted with due sanitary precautions, and all viruses, 
serums, toxins, or analogous products shipped or deliv- 
ered for shipment shall be securely packed. 

Section 2. Paragraph 1. The floors, walls, ceilings, 
partitions, posts, doors, and all other parts of all struc- 
tures at licensed establishments shall be of such material, 
construction, and finish as can be readily and thoroughly 
cleaned. 

Paragraph 2. Separate rooms or compartments shall 
be provided for preparing, handling, and storing viru- 
lent or attenuated micro-organisms or toxins. 

Paragraph 3. All rooms and compartments shall have 
abundant light and sufficient ventilation to insure sani- 
tary and hygienic conditions. 

Section 3. Paragraph 1. Each licensed establish- 
ment shall have dressing rooms and toilet rooms and 
urinals sufficient in number, ample in size, conveniently 
located, properly ventilated, and meeting all require- 
ments as to sanitary construction and equipment. These 
shall be separate from rooms and compartments in which 
any viruses, serums, toxins, or analogous products are 
prepared, handled, or stored. 

Paragraph 2. Each licensed establishment shall have 
modern lavatory accommodations, including running hot 
and cold water, soap, towels, and the like. These shall 
be located at such places in establishments as may be 



260 HOG CHOLERA 

essential to assure cleanliness of all persons handling 
viruses, serums, toxins, or analogous products. 

Section 4. There shall be an efficient drainage and 
plumbing system for the establishment and premises, 
and all drains and gutters shall be properly installed 
with approved traps and vents. 

Section 5. The water supply, both hot and cold, shall 
be ample and clean. Adequate facilities shall be pro- 
vided for the distribution of water in each establish- 
ment and for the washing of all equipment, containers, 
machinery, instruments, other apparatus, and animals 
used in the preparation, handling, or storing of any 
viruses, serums, toxins, or analogous products. 

Section 6. All equipment, containers, instruments, 
and other apparatus used in the preparation, handling, 
or storing of any virus, serum, toxin, or analogous prod- 
uct shall be of such material, construction, and design 
as can be readily and thoroughly cleaned and sterilized, 
and such equipment, containers, instruments, and other 
apparatus shall be handled so as to insure freedom from 
contamination. Equipment, containers, instruments, and 
other apparatus used for preparing, handling, or stor- 
ing virulent or attenuated micro-organisms or toxins 
shall not be used for handling, preparing, Or storing 
other forms of biological products. 

Section 7. All emploj^ees of the establishment who 
handle viruses, serums, toxins, or analogous products 
shall keep their hands and clothing clean. The hands 
of such employees shall not come into contact with any 
viruses, serums, toxins, or analogous products, or with 
any part of the equipment, containers, instruments, or 
other apparatus, which after sterilization may come into 
contact with any such products. 

Section 8. Caps, gowns, and other outer clothing 
worn by persons while handling any viruses, serums, 
toxins, or analogous products, or by those who enter 



APPENDIX 261 

any room, compartment, or place where any such prod- 
ucts are being handled, shall be of clean, white material 
whenever practicable. 

Section 9. The outer premises of every licensed es- 
tablishment, embracing docks, driveways, approaches, 
yards, pens, chutes, and alleys, shall be properly drained 
and kept in a clean and orderly condition. The accumu- 
lation on the premises of an establishment of any ma- 
terial in which flies may breed is forbidden. No nuisance 
shall be allowed in any licensed establishment or on its 
premises. 

Section 10. Every practicable precaution shall be 
taken to keep establishments free of flies, rats, mice, and 
other vermin. 

Section 11. All parts of the carcasses of animals pro- 
ducing viruses, all dead animals, all refuse, and all 
worthless, contaminated, dangerous, or harmful viruses, 
serums, toxins, or analogous products, shall be inciner- 
ated or otherwise destroyed by establishments in accord- 
ance with methods approved by the chief bureau. 

Section 12. All rooms, compartments, and other 
places used for preparing, handling, or storing viruses, 
serums, toxins, or analogous products shall be kept clean 
and sanitary, and all equipment, containers, instruments, 
and other apparatus used in joreparing, handling, or 
storing any such products shall be thoroughly cleaned 
and sterilized before use. 

Section 13. Smoking or expectorating in any room, 
compartment, or place in which viruses, toxins, or analo- 
gous products are prepared, handled, or stored is pro- 
hibited. 

regulation 9. — sterilization 

Section 1. Paragraph 1. All equipment, containers, 
instruments, and other apparatus, before being used in 
preparing, handling, or storing viruses, serums, toxins, 
or other analogous products, except as prescribed in the 



262 HOG CHOLERA 

following paragraph, shall be thoroughly sterilized by 
live steam at a temperature of at least 120° C. for not 
less than one-half hour, or, by dry heat at a temperature 
of at least 160° C. for not less than one hour. If for any 
reason such methods of sterilization are impracticable, 
then a process known to be equally efficacious in de- 
stroying microorganisms and their spores may be sub- 
stituted after approval by the chief of bureau. 

Paragraph 2. Instruments used in connection with 
the bleeding of virus pigs and hyperimmune hogs, and 
other like equipment, of establishments manufacturing 
hog-cholera virus and anti-hog-cholera serum, which are 
found to be damaged by exposure to the degree of heat 
prescribed in the preceding paragraph, after having been 
thoroughly cleaned, may be sterilized by boiling for not 
less than 15 minutes, provided apparatus, satisfactory 
to the inspector in charge, is furnished for this purpose. 

REGULATION 10. — STORAGE 

Section 1. Viruses, serums, toxins, and analogous 
products which may be injuriously affected by exposure 
to light or to high temperature shall be stored in a dark, 
cold chamber or refrigerator at a temperature of not to 
exceed 55° F. All dealers in the District of Columbia 
or any Territory or in any place under the jurisdiction 
of the United States shall keep such products protected 
from light and under refrigeration until sold or other- 
wise disposed of. 

REGULATION 11. — RECORDS 

Section 1. Paragraph 1. Permanent detailed rec- 
ords of the sources, of the preparation, of tests for purity 
and potencj^, and of methods of preservation, of each 
batch of virus, serum, toxin, and analogous products 
shall be kept by each licensed establishment and by each 



APPENDIX 263 

manufacturer producing such products for importation 
into the United States. 

Paragraph 2. Permanent detailed records, in a form 
satisfactory to the chief of bureau, shall be maintained 
by each licensed establishment and by each importer, 
showing the sale, shipment, or other disposition of the 
viruses, serums, toxins, and analogous products handled. 

REGULATION 12. — LABELS 

Section 1. Paragraph 1. Each immediate or true 
container of viruses, serums, toxins, or analogous prod- 
ucts, prepared for sale, barter, exchange, or shipment, 
by any licensed establishment, or imported into the 
United States, shall bear a trade label as hereinafter de- 
scribed. 

Paragraph 2. No container of virus, serum, toxin, or 
analogous product shall bear a trade label unless and 
until the product contained therein shall have been pre- 
pared in compliance with these regulations and found 
not to be worthless, contaminated, dangerous, or harm- 
ful. 

Paragraph 3. No person shall apply or affix, or cause 
to be applied or affixed, any trade label, stamp, or mark, 
to any container of hog-cholera virus, or anti-hog- 
cholera serum, prepared or received in a licensed estab- 
lishment except in compliance with these regulations. 
Suitable tags or labels of a distinct design should be 
used for identifying all biologies while in course of 
preparation. 

Section 2. Paragraph 1. Trade labels shall bear the 
true name of the product contained in the package, the 
name and address of the manufacturer except as other- 
wise provided in paragraph 7 of this section, and the 
license or permit number assigned by the department. 
The license number and permit number shall be shown 
in either of the following forms, respectively: "U. S. 



264 HOG CHOLEEA 

Veterinary License No. ," or ''U. S. Vet. License 

No. ," and ''U. S. Veterinary Permit No. ," 

or ''U. S. Vet. Permit No. ." Such labels shall bear 

all other information required by the chief of bureau and 
may also bear any other statement not false or mislead- 
ing and which has been approved by the bureau. 

Paragraph 2. Each trade label shall bear a serial 
number, affixed by the manufacturer, by which the prod- 
uct can be identified with the records of preparation. 

Paragraph 3. Each trade label shall bear a return 
date affijxed before the product is removed from the 
establishment. The date shown shall be a date after 
which the manufacturer does not guarantee the product 
to be of full strength or potency. 

Paragraph 4. All trade labels affixed to or used in 
connection with each immediate or true container shall 
bear a dosage table and full instructions governing the 
use of the product. 

Paragraph 5. Trade labels affixed to the immediate 
or true containers of viruses and products prepared 
from attenuated organisms shall bear, in addition to the 
statements required by the preceding paragraphs of this 
section, the following, prominently placed and lettered: 
''Caution — Burn this Container and all Unused 
Contents. ' ' 

Paragraph 6. When any virus, serum, toxin, or analo- 
gous product is prepared by a licensed establishment or 
imported for a person other than the one to whom a 
license or permit has been issued and the name and ad- 
dress of the distributor as well as that of the manufac- 
turer is to appear on the label of the container thereof, 
a statement shall be made on the label to the effect that 
the virus, serum, toxin, or analogous product is dis- 
tributed by such person. The term, ''Distributer/' 
"Distributers," "Distributed by," or other equivalent 
terms may be used, if prominently ^placed and lettered 



APPENDIX 265 

in connection with the name and address of the distrib- 
uting person, provided the same are not used so as to be 
either false or misleading. 

Paragraph 7. The name and address of the manufac- 
turer may be omitted from trade labels when any virus, 
serum, toxin, or analogous product is to be distributed by 
a person other than the manufacturer, provided the 
name and address of the distributor appears on such 
trade labels in immediate connection with a statement 
showing the license under which the product was manu- 
factured. This statement, together with the name and 
address of the distributor, shall appear in letters of uni- 
form size and character, and be in the following form: 
''Produced under U. S. Veterinary License No, — — . 
Distributed by (name and address of distributor)." 

Paragraph 8. Copies of all trade labels before use 
shall be submitted to the bureau for examination and 
approval. These labels shall be submitted in triplicate, 
quadruplicate, or quintuplicate, as may be indicated. 
Triplicate copies of new trade labels in the form of 
sketches, proofs, or photographic copies should be sub- 
mitted, through the inspector in charge, to the bureau 
for approval. 

REGULATION 13. — COLLECTING SAMPLES 

Section 1. Paragraph 1. Samples of viruses, serums, 
toxins, and analogous products* shall be collected by au- 
thorized officers, agents, or employees of the department. 

Paragraph 2. Samples may be purchased in the open 
market and the marks, brands, or tags upon the package 
or wrapper thereof shall be noted. The collector shall 
note the names of the vendor and agent of the vendor 
who made the sale, together with the date of purchase. 
The collector shall purchase representative samples. 

Paragraph 3. All samples or parts of samples shall be 
sealed by the collector and marked with identifying 
marks. 



266 HlOG CHOLEKA 

REGULATION 14. — TESTING 

Section 1. Except as otherwise provided in these 
regulations, all viruses, serums, toxins, and analogous 
products shall be prepared, handled, stored, marked, 
treated, and tested by licensed establishments in accord- 
ance with methods prescribed by the Chief of the Bu- 
reau of Animal Industry. 

regulation 15. — retesting 

Section 1. Viruses, serums, toxins, and analogous 
products, the containers of which bear United States 
veterinary license numbers or United States veterinary 
permit numbers, or any other mark required by these 
regulations, shall be subject to inspection at any time or 
place. If it appears as a result of such inspection that 
any such product, even though prepared in a licensed 
establishment or imported under permit issued by the 
Secretary, is worthless, contaminated, dangerous, or 
harmful, the Secretary shall give notice thereof to the 
manufacturer or importer and to any jobbers, dealers, 
or other persons known to have any of such product in 
their possession. Unless and until the Secretary shall 
otherwise direct, no person so notified shall thereafter 
sell, barter, or exchange in any place under the jurisdic- 
tion of the United States nor shall thereafter ship or 
deliver for shipment from any States, Territory, or the 
District of Columbia to any other State, Territory, or 
the District of Columbia, any of such product. 

regulation 16. — REPORTS 

Section 1. Paragraph 1. Reports of the work of in- 
spection carried on in every licensed establishment shall 
be forwarded to the bureau by the inspector in charge 
in such form and manner as may be specified by the 
chief of bureau. 



APPENDIX 267 

Paragraph 2. Each licensed establishment shall fur- 
nish to the bureau employees accurate information as to 
all matters needed by them for making their reports 
pursuant to paragraph 1 of this section. 

REGULATION 17. — ANIMALS 

Section 1. Paragraph 1. Licensed establishments 
which procure animals from public stockyards, abattoir 
pens, or similar places shall afford opportunity for all 
hogs, cattle, sheep, and goats admitted to the premises 
of such establishments to range in contact with other 
animals as prescribed in section 3 of this regulation. 

Paragi^aph 2. Cattle, sheep, and goats from whatever 
source, except calves procured under the provisions of 
section 5 of this regulation and used for testing hog- 
cholera virus to determine its freedom from foot-and- 
mouth disease, admitted to the premises of licensed es- 
tablishments shall be afforded opportunity to range in 
contact with other animals as prescribed in section 3 of 
this regulation. 

Section 2. Paragraph 1. Licensed establishments 
shall provide suitable pens to be known as '^Receiving 
pens" through which all hogs, cattle, sheep, and goats 
shall pass in accordance with the provisions of this 
regulation before they shall be admitted to any other 
part of the premises. 

Paragraph 2. Licensed establishments shall provide 
healthy calves in thrifty condition and ranging from 3 
to 12 months of age for use as contact animals in re- 
ceiving pens. They shall be referred to as ^'contact 
calves." 

Paragraph 3. Each contact calf shall have the left 
ear thereof pierced with a hole not less than % inch in 
diameter and to the right ear of each animal shall be 
attached a serially numbered metal tag. 

Section 3. Paragraph 1. All hogs susceptible to hog 



268 HOG CHOLEKA 



i 



cholera which are admitted to the premises of licensed 
establishments under the provisions of section 1, para- 
graph 1, of this regulation shall be held in receiving 
pens for at least 24 hours after admission to the premises 
and during this time they shall be allowed free range 
and contact with not less than 4 contact calves for each 
lot of 200 hogs or less in the receiving pens. 

Paragraph 2. Hogs which are immune to hog cholera, 
admitted to the premises of licensed establishments un- 
der the provisions of section 1, paragraph 1, of this 
regulation, shall be held in receiving pens with contact 
calves as prescribed in the preceding paragraph for at 
least 48 hours. 

Paragraph 3. All animals covered by section 1, of this 
regulation, except hogs, shall be held in receiving pens 
for at least 48 hours as prescribed in paragraph 1, of 
this section, except that not less than two contact calves 
shall be used for each lot of 20 animals or less in the 
same pen. 

Section 4. Paragraph 1. All surviving contact calves 
shall be held in the receiving pens of licensed establish- 
ments for at least one month and not to exceed four 
months from date of admission to receiving pens as 
contact calves. 

Paragraph 2. Kemoval of contact calves from receiv- 
ing pens shall be so arranged that a rotation will be es- 
tablished whereby one of the animals will be replaced at 
intervals of one month and the entire group replaced 
every four months or less. 

Paragraph 3. Removal of contact calves from receiv- 
ing pens shall be accomplished so that the animals last 
furnished for the purpose may be used for the maximum 
time permitted by the preceding paragraphs of this 
section. No contact calf shall be used as such more than 
once. 

Paragraph 4. Contact calves shall be carefully ob- 



APPENDIX 269 

served by a veterinary inspector as frequently as may 
be necessary to detect evidence of disease. 

Section 5. Establishments licensed to prepare anti- 
hog-cholera serum or hog-cholera virus which do not 
procure animals from public stockyards, abattoir pens, 
or similar places, shall furnish a properly executed cer- 
tificate according to the following form covering each 
lot or shipment of animals offered for admission to the 
premises thereof. These certificates shall be signed by 
an authorized representative of the licensed establish- 
ment. 

,19--. 

This is to certify that , 



/ Calves [ '^^i^^^ ^^^ offered for admission to the estab- 
lishment of the Company, are 

from the farm or premises of , in the 

State of , county of , town- 
ship of , and to the best of our 

knowledge and belief were on said farm or premises at 
least 21 days prior to this date, and were not exposed to 
any infectious, contagious, or communicable disease, and 
no new stock was brought on to the said farm or premises 
during that time. The said animals have not been in or 
transported through any public stockyards, abattoir 
pens, or similar places, nor have they been exposed to 
any infectious, contagious, or communicable disease since 
their removal from said farm or premises. 

(Signed) Co., 

Per 



Section 6. Paragraph 1. All animals presented for 
admission to the premises of establishments licensed to 
prepare hog-cholera virus or anti-hog-cholera serum shall 
be examined by a veterinary inspector as soon as prac- 
ticable after they are received and before their re- 
moval from the receiving pens in order to determine 



270 HOG CHOLEEA 

their physical condition. No animal shall be removed 
from receiving pens without examination by and the 
permission of a veterinary inspector. 

Paragraph 2. After examination, if the animals are 
permitted to remain upon the premises and to gain en- 
trance to the holding pens of the establishment, they 
shall be given serially numbered metal tags, either prior 
to or at the time of inoculation or hyperimmunization. 

Paragraph 3. All tags used for the identification of 
animals shall be attached to the ears of the animals in 
a manner satisfactory to the inspector in charge. The 
tags so attached shall be the means of assisting in identi- 
fying the animals so long as they remain on the premises. 

Paragraph 4. All tags which are used to identify ani- 
mals shall be furnished and attached by the licensed 
establishment, and when said tags are not in actual use 
they shall at all times be held in the custody of a bureau 
employee. 

Paragraph 5. When practicable, the left ear of each 
animal used in testing the purity and potency of viruses, 
serums, toxins, and analogous products shall be pierced 
with a hole not less than three-fourths of an inch in 
diameter. Animals bearing marks of the above-de- 
scribed character shall not be used more than once by 
licensed establishments in testing the purity and po- 
tency of any virus, serum, toxin, or analogous product. 
Furthermore, animals Avith the left ear removed or 
mutilated so as to prevent the detection of this identi- 
fying mark shall not be used in any test. 

Section 7. Animals used in the production or testing 
of viruses, serums, toxins, or analogous products shall 
not be treated with biological products other than those 
which are incidental to the preparation and testing of 
the products prepared from or tested upon said animals, 
except with the approval of and in such manner as may 
be prescribed by the chief of bureau. 



APPENDIX 271 

Section 8. Paragraph 1. If for any reason hyper- 
immune hogs are practically the only animals held upon 
the premises of a licensed establishment, they shall be 
caused to range in contact with calves in the manner 
prescribed in section 3 of this regulation for a period of 
at least 10 days prior to their being subjected to carotid 
or final bleeding. 

Paragraph 2. All animals with which hyperimmune 
hogs have been held in contact as prescribed in this sec- 
tion, shall be held on the premises of the licensed estab- 
lishment and under the observation of a bureau employee 
for at least two weeks after the hyperimmune hogs have 
been destroyed. 

Paragraph 3. All hyperimmune hogs which are sub- 
jected to the tail-bleeding process only, shall be held 
under the supervision of a bureau employee for at least 
two weeks after the last tail bleeding has been col- 
lected. 

Section 9. Paragraph 1. Establishments licensed to 
prepare hog-cholera virus and anti-hog-cholera serum 
shall not remove either hogs or calves from the premises 
of the establishment without written permission obtained 
in advance from the inspector in charge. 

Paragraph 2. Permission for the removal of hogs or 
calves from the premises of licensed establishments for 
the purpose of immediate slaughter shall be given by the 
inspector in charge under the following conditions : 

{a) Wlien such animals are found not to be affected 
with any disease or condition that may render them in 
whole or in part unfit for food purposes. 

(Z>) When such animals are found to be affected with 
any disease or condition which maj^ render them unfit 
for food purposes in whole or in part, provided said 
animals are slaughtered at an establishment where Fed- 
eral meat inspection is maintained, and provided fur- 
ther, that the inspector in charge of meat inspection 



272 HOG CHOLERA 

where said animals are to be slaughtered is given due 
notice thereof. 

Paragraph 3. Permission for the removal of hogs or 
calves from the premises of licensed establishments for 
purposes other than immediate slaughter shall be given 
by the inspector in charge under the following condi- 
tions: 

{a) Calves may be removed if found to be free from 
any infectious, contagious, or communicable disease, 
provided the feet and legs of calves used for testing 
hog-cholera virus or anti-hog-cholera serum are cleaned 
and disinfected with a 2 per cent aqueous solution of 
cresol compound, U. S. P., or a permitted substitute 
therefor and the animals held in noninfectious pens on 
the premises of the establishment for at least three hours 
before being loaded for transportation. 

(&) Hogs which survive inoculation and exposure for 
the production of hog-cholera virus, surviving controls 
from tests of anti-hog-cholera serum, and surviving hogs 
which have been used for testing hog-cholera virus may 
be removed from the premises of the establishment not 
sooner than 15 days subsequent to the day of inocula- 
tion and exposure, provided they are healthy. It is 
required, however, that all such hogs before their re- 
moval from the premises be given the serum-alone treat- 
ment as prescribed under {a) of paragraph 4 of this 
section. Hyperimmune hogs and pigs used for testing 
the purity and potency of anti-hog-cholera serum may 
be removed from the premises of licensed establishments 
21 days subsequent to the day of hyperimmunization or 
inoculation, provided they exhibit no symptoms of any 
infectious, contagious, or communicable disease and pro- 
vided further that they are first disinfected as provided 
in paragraph 4 of this section. Other hogs shall be 
removed from the premises of the establishment only 
after treatment and disinfection as provided in para- 



APPENDIX 273 

graph 4 of this section, except that such hogs need not 
be held 21 days when treated with serum and virus 
which have been released for marketing. 

Paragraph 4. Hogs which require treatment as pro- 
vided under (&) in paragraph 3 of this section shall be 
treated and disinfected as follows: 

{a) Serum-alone method. — The serum used shall have 
been prepared and released for marketing at an estab- 
lishment holding a license from the Secretary of Agri- 
culture and the dose employed shall conform to that re- 
quired in paragraph 1, section 6, or paragraph 3, sec- 
tion 10 of Regulation 19. After receiving this treatment 
they shall be disinfected by dipping in a 2 per cent 
aqueous solution of cresol compound, U. S. P., or a per- 
mitted substitute therefor, except when prevailing low 
temperatures make it impracticable, and be held in non- 
infectious pens for at least 3 hours before being loaded 
for transportation. 

(&) Simiiltaneous-inoculation method. — The serum 
and virus used shall have been prepared at an establish- 
ment holding a license from the Secretary of Agriculture 
and the doses shall be not less than those required in 
paragraph 1, section 6, or paragraph 3, section 10 of 
Regulation 19. After receiving this treatment they shall 
be held under the supervision of a bureau employee for 
a period of at least 21 days, except when treated with 
virus and serum released for marketing. If no symp- 
toms of hog cholera or other infectious, contagious, or 
communicable disease are exhibited by the animals, they 
shall be disinfected by dipping in a 2 per cent aqueous 
solution of cresol compound, U. S. P., or a permitted 
substitute therefor, except when prevailing low tempera- 
tures make it impracticable, and held in noninfectious 
pens for a period of at least 3 hours before being loaded 
for transportation. 

Section 10. Except as otherwise provided in these 



274 HOG CHOLERA 

regulations, all animals used by licensed establishments 
in the preparation or testing of veterinary biologies shall 
meet such requirements as may be prescribed by the 
Chief of the Bureau of Animal Industry and deemed by 
him necessary to prevent the preparation and sale of any 
worthless, contaminated, dangerous, or harmful viruses, 
serums, toxins, or analogous products. 

Section 11. Each licensed establishment shall adopt 
such measures as the chief of bureau shall from time to 
time prescribe for carrying out the provisions of this 
regulation. 

REGULATION 18. — HOG-CHOLERA VIRUS 

Section 1. Paragraph 1. All operations incident to 
the production of hog-cholera virus shall be conducted 
under the supervision of a bureau employee. Each 
licensed establishment shall notif}^ the inspector in 
charge or his assistant a reasonable time in advance when 
any operations are to be conducted. 

Paragraph 2. Pigs which are used in the production 
of hog-cholera virus shall be healthy and the tempera- 
ture of each animal shall be accurately taken and per- 
manently recorded by the establishment immediately be- 
fore inoculation when in the opinion of the inspector in 
charge this is necessary to determine the health of the 
animals. Each animal shall be subjected to a careful 
examination by a veterinary inspector immediately prior 
to inoculation. 

Paragraph 3. Temperatures of all pigs used to pro- 
duce hog-cholera virus shall be correctly taken and re- 
corded by licensed establishments each day subsequent 
to the fifth day after inoculation and at such other times 
as the inspector in charge may deem necessary. The 
temperature of each pig invariably shall be taken and 
recorded on each day the animal is found to be visibly 
sick. 



APPENDIX 275 

Paragraph 4. Pigs which have been inoculated for 
the production of hog-cholera virus shall be killed for 
this purpose only after a veterinary inspector has ob- 
served well-marked symptoms of hog cholera. 

Paragraph 5. All pigs from which hog-cholera virus 
is derived shall be subjected to a post-mortem examina- 
tion by a veterinary inspector. 

Paragraph 6. Hog-cholera virus derived from pigs 
which become visibly sick within three days after the 
time they are admitted to the premises of licensed estab- 
lishments shall be destroyed as provided in section 11, 
Regulation 8, under the supervision of a bureau em- 
ployee. 

Paragraph 7. Hog-cholera virus derived from pigs 
which upon post-mortem examination do not show le- 
sions of acute hog cholera or which are found to be so 
affected with any infectious, contagious, or communi- 
cable disease or in such condition as to render the virus 
contaminated, shall be destroyed as provided in section 
11, Regulation 8, under the supervision of a bureau 
employee. A diagnosis of hog cholera will not be made 
unless macroscopic lesions of the disease are found in 
two or more organs or tissues. 

Paragraph 8. Hog-cholera virus derived from pigs 
which are found to be affected with tuberculosis shall be 
destroyed as provided in section 11, Regulation 8, under 
the supervision of a bureau employee, unless the lesions 
are slight or are localized, and are calcified or encapsu- 
lated. Hog-cholera virus derived from pigs so affected 
may be marketed only when the product is heated as 
provided in paragraph 6, section 3, of this regulation. 

Paragraph 9. All records shall indicate clearly the 
particular animal, or group of animals, from which each 
batch of hog-cholera virus is derived. The amount col- 
lected and the total amount after phenolization should 
be separately recorded. 



276 HOG CHOLERA 

Paragraph 10. Hog-cholera virus shall not be re- 
moved from the premises of a licensed establishment un- 
less the virus has been prepared in accordance with the 
provisions of these regulations. 

Paragraph 11. No immediate or true container of 
hog-cholera virus shall be filled in whole or in part, and 
no trade label shall be affixed to such containers except 
under the supervision of a bureau employee. 

Paragraph 12. The following special facilities, and 
such others as may be required by the chief of bureau, 
shall be provided by each establishment licensed to pre- 
pare hog-cholera virus: 

(a) Separate operating rooms. 

(6) A separate room in which the animals shall be 
washed, cleaned, and otherwise prepared before being 
taken into the operating room. 

(c) A separate room for conducting autopsies. 

(cZ) A separate room for the preparation and mixing 
of virus. 

(e) A separate room for washing and sterilizing 
equipment. 

(/) Clean cloths which shall be kept damp when in 
use, to be used for covering pigs during all operations 
incident to the collection of hog-cholera virus. 

{g) All outside screens, openings, and windows shall 
be equipped with dust screens. 

Paragraph 13. All persons, immediately before en- 
tering the operating or laboratory rooms of an establish- 
ment licensed to prepare hog-cholera virus, shall change 
their outer clothing or cover it by the use of clean 
gowns, or other satisfactory garments. 

Section 2. Paragraph 1. For use in the production 
of hyperimmunizing virus, licensed establishments shall 
inoculate young pigs weighing not more than 145 pounds 
each with at least 2 cubic centimeters of a virulent strain 
of hog-cholera virus. 



APPENDIX 277 

Paragraph 2. Hyperimmunizing virus prepared in 
accordance with sections 1 and 2 of this regulation may 
be transported from one licensed establishment to an- 
other under bureau seal, provided the product is prop- 
erly iced and its transfer is accomplished in such man- 
ner and by such methods as shall be approved by the 
chief of bureau. 

Section 3. Paragraph 1. For use in the production 
of simultaneous virus, licensed establishments shall in- 
oculate young pigs weighing not less than 40 pounds, 
nor more than 100 pounds each with at least two 
cubic centimeters of a virulent strain of hog-cholera 
virus. 

Paragraph 2. Simultaneous virus shall not be col- 
lected from pigs which become visibly sick on or before 
the fourth day, or subsequent to the seventh day after 
the time of inoculation. The physical condition of pigs 
from which simultaneous virus is collected shall be re- 
corded daily on and after the fourth day subsequent to 
inoculation. 

Paragraph 3. Simultaneous virus shall be collected 
only from pigs which exhibit visible symptoms of hog 
cholera within seven days, and are visibly sick of this 
disease to a degree sufficient to result in death within 
15 days after the time of inoculation. 

Paragraph 4. Pigs which have been inoculated for 
the production of simultaneous virus shall be killed only 
after permission has been obtained from an authorized 
bureau employee. 

Paragraph 5. Simultaneous virus shall be defibri- 
nated promptly after collection, and immediately there- 
after chilled and maintained at a temperature not to 
exceed 55° F. (12.8° C). 

Paragraph 6. When simultaneous virus is heated it 
shall be done under the supervision of a bureau employee 
and in such manner as to subject the product and the 



278 ^ HOG CHOLERA 

entire container thereof to a temperature ranging from 
50° to 50.5° C. for 12 hours. 

Paragraph 7 . Simultaneous virus which has been 
heated, as provided in the preceding paragraphs, shall 
not be handled thereafter in a manner which will ex- 
pose the product to contamination. 

Paragraph 8. AVhen simultaneous virus is heated, as 
described in paragraph 6 of this section, and tested upon 
pigs, as hereinafter provided, the product need not be 
tested upon calves. 

Paragraph 9. When simultaneous virus is heated, each 
batch shall be tested for virulence by inoculating intra- 
muscularly, with two cubic centimeters of virus, each 
of two pigs which are susceptible to hog cholera. Should 
the pigs thus inoculated exhibit visible symptoms of hog 
cholera, as required for pigs inoculated to furnish simul- 
taneous virus, the virus under test may be marketed. 

Paragraph 10. Pigs selected for testing the virulence 
of heated simultaneous virus shall be inoculated imme- 
diately after their admission to the premises. The quar- 
ters where these pigs are held during the test shall be 
isolated as completely as feasible from quarters occu- 
pied by other pigs sick of hog cholera. All reasonable 
precautions shall be taken to prevent infection of these 
pigs from sources other than by inoculation. Such pre- 
cautions shall include a thorough cleaning and disinfec- 
tion of the pen in which the pigs are held during the 
test, and a disinfection of these animals after they are 
placed in a holding pen. The disinfection of these pens 
and the test pigs shall be accomplished by such methods 
as shall be approved by the chief of bureau. 

Section 4. Paragraph 1. Simultaneous virus shall be 
collected in batches of not to exceed 20,000 cubic centi- 
meters each and each batch shall be mixed thoroughly in 
a single container. 

Paragraph 2. After mixing, but before phenoliza- 



APPENDIX 279 

tion, a representative sample of each batch, consisting of 
at least 15 cubic centimeters of the mixture, shall be 
taken by a bureau employee. This sample shall be known 
as the ' ' Virus-test sample. ' ' 

Paragraph 3. Simultaneous virus which has been 
mixed as provided in this section, after withdrawal of 
the '* Virus-test sample," shall have added to it a suffi- 
cient quantity of a 5 per cent solution of phenol so that 
the virus will contain one-half of. 1 per cent phenol by 
volume. This phenolization must be accomplished Avith 
accuracy and in a manner which will prevent undesir- 
able changes in the product. After thorough mixing in a 
single container, a representative sample, consisting of 
at least 100 cubic centimeters, collected in three contain- 
ers, shall be taken by a bureau employee. This sample 
shall be known as the "Virus-stock samj^le." 

Paragraph 4. Simultaneous virus which has been 
mixed and phenolized, as provided in this section, to- 
gether with the virus-stock sample and the unused resi- 
due of the virus-test sample, shall be placed under bu- 
reau lock and held as provided under (5), section 1 of 
Regulation 7 until su,ch time as the tests have shown 
the batch of virus to be virulent and free from contami- 
nation. 

Paragraph 5. At least one container of the virus-stock 
sample shall be held unopened under bureau lock, in the 
manner provided in Regulation 7, for at least three 
months after the expiration of the latest return date 
shown upon the trade labels affixed to the immediate or 
true containers of the product corresponding to the 
virus-stock sample. Unless the virus is heated as pro- 
vided in paragraph 6, section 3, of this regulation the 
virus-test sample described in paragraph 2 of this sec- 
tion shall be used to determine the freedom from con- 
tamination of each batch of simultaneous virus. 

Paragraph 6. Two healthy calves, with mouths free 



280 HOG CHOLERA 

from abrasions, and not less than 3 nor more than 12 
months old, shall be furnished by the establishment for 
the inoculation with the virus-test sample. 

Paragraph 7. All animals used for the testing of 
simultaneous virus shall be inoculated only under the 
supervision of a veterinary inspector, and shall be 
marked as provided in paragraphs 2, 3, 4, and 5, section 
6 of Regulation 17. 

Paragraph 8. Each of the calves selected for testing 
the purity of simultaneous virus shall be inoculated by 
injecting 5 cubic centimeters of the virus-test sample 
into either the auricular or jugular vein Avithin 24 hours 
after the virus is collected. 

Paragraph 9. Calves inoculated for the purpose of 
determining the purity of simultaneous virus as pro- 
vided in the preceding paragraph shall be held under 
the observation of a veterinary inspector for a period of 
at least 7 days. Should foot-and-mouth disease appear 
in the United States the said calves shall be held under 
the observation of a veterinary inspector for 10 days 
or longer, in the discretion of the inspector in charge. 

Paragraph 10. Simultaneous virus which has been 
either heated, as provided in paragraph 6, section 3 of 
this regulation, or subjected to the test prescribed in 
paragraph 8, section 4 of this regulation, may be re- 
leased for marketing, provided the animals treated with 
the virus remain well and develop no symptoms of any 
infectious, contagious, or communicable disease. 

Paragraph 11. Simultaneous virus found to be worth- 
less or contaminated shall be destroyed as provided in 
section 11, Regulation 8, under the supervision of a 
bureau employee. 

Section 5. Paragraph 1. Each immediate or true 
container of simultaneous virus which has been tested 
and found not to be worthless or contaminated shall bear 
a stamp or mark approved by the department. Such 



APPENDIX 281 

stamp or mark shall bear the phrase ''U, S. Released." 
Each container of simultaneous virus shall be appropri- 
ately sealed with a suitable material and the aforesaid 
stamp or mark securely affixed to the sealing material 
under the supervision of a bureau employee. Should 
any difficulty result from the action of moisture upon 
said stamp or mark, causing it to become detached or 
illegible, that portion of the container which has been 
sealed and stamped shall be subjected at once to dipping 
in hot paraffin or other waterproof material. 

Paragraph 2. The trade label on each immediate or 
true container of simultaneous virus shall bear the date 
of manufacture, which date shall be the day on which 
the virus is collected. 

Paragraph 3. The return date placed upon the label 
of each immediate or true container of simultaneous 
virus shall be a date within 60 days after the date of 
manufacture. 

Paragraph 4. Trade labels affixed to or used in con- 
nection with the immediate or true containers of hog- 
cholera virus shall plainly show the amount of the con- 
tents of said containers. 

Paragraph 5. Trade labels affixed to or used in con- 
nection with each immediate or true container of simul- 
taneous virus shall bear a dosage table in which the doses 
recommended are not less than those appearing in the 
following table: 

Weight. Minimum dose. 

Pigs weighing 100 pounds or less 1 c. c. 

Hogs weighing more than 100 pounds. . . 2 c. c. 

Paragraph 6. No hog-cholera virus shall be released 
for marketing unless and until all information required 
by these regulations has been affixed to the containers 
thereof under the supervision of a bureau employee. 



282 HOG CHOLEKA 

REGULATION 19. ANTI-HOG-CHOLERA SERUM 

Section 1. All operations incident to the production 
of anti-hog-cholera serum shall be conducted under the 
supervision of a bureau employee. Each licensed estab- 
lishment shall notify the inspector in charge, or an as- 
sistant, a reasonable time in advance when any opera- 
tions are to be conducted. 

Section 2. Paragraph 1. Anti-hog-cholera serum 
shall be derived only from hyperimmune hogs which 
have been immune to hog cholera for at least 60 days 
prior to hyperimmunization. 

Paragraph 2. Anti-hog-cholera serum shall be derived 
only from hyperimmune hogs which have been subjected 
to not more than 4 successive bleedings after each hyper- 
immunization. The first bleeding shall take place not 
earlier than 10 daj^s after hyperimmunization, subse- 
quent bleedings shall not take place more frequently 
than once in 7 days, and the last bleeding shall be made 
on a date not later than 38 days after hyperimmuniza- 
tion. 

Paragraph 3. Hogs which are used to produce anti- 
hog-cholera serum shall be healthy at the time of hyper- 
immunization, this fact to be determined by a careful 
examination made by a veterinary inspector prior to 
hyperimmunization. The temperature and weight of 
each animal shall be accurately obtained and recorded 
by tlie establishment before hyperimmunization. 

Paragraph 4. All hogs which are used to produce 
anti-hog-cholera serum shall receive a single intravenous 
injection of at least 5 cubic centimeters of hog-cholera 
virus for each pound of the animal 's weight. 

Paragraph 5. Temperature of all hogs used to pro- 
duce anti-hog-cholera serum shall be accurately taken 
and recorded by licensed establishments, either on the 
afternoon before or on the day of bleeding, and at such 



APPENDIX 283 

other times as the inspector in charge may deem neces- 
sary. All temperatures shall be taken under normal 
conditions so far as possible and in a manner which will 
expedite the work. 

Paragraph 6. All hogs which are used to produce 
anti-hog-cholera serum shall be subjected to a careful 
examination by a veterinary inspector immediately prior 
to each bleeding. Only those hogs shall be bled for 
serum which are found to have a temperature of less 
than 104° F. and are free from infectious, contagious, 
or communicable diseases or other harmful conditions. 

Paragraph 7. All hogs from which anti-hog-cholera 
serum is derived shall be subjected to a post-mortem ex- 
amination by a veterinary inspector, except as herein- 
after provided, and if, as a result of such examination, 
it is found that any hog is so affected with any infec- 
tious, contagious, or communicable disease, or is in such 
condition as to render the serum worthless, contami- 
nated, dangerous, or harmful, the serum collected from 
such hogs shall be destroyed by the establishment as pro- 
vided in section 11, Regulation 8, under the supervision 
of a bureau employee. Serum derived from hogs which 
are found to be affected with tuberculosis need not be 
destroyed, provided the lesions are slight or are localized, 
and are calcified or encapsulated. 

Paragraph 8. Anti-hog-cholera serum derived from 
each hyperimmune hog shall be kept separate and apart 
from other serum except when heated as prescribed in 
paragraph 10 of this section, until it has been determined 
by post-mortem examination that the hog from which 
the serum is derived is not so affected with any infec- 
tious, contagious, or communicable disease or is in such 
condition as to render the serum worthless, contami- 
nated, dangerous, or harmful. 

Paragraph 9. When anti-hog-cholera serum is heated 
as described in the following paragraph, the serum de- 



284 HOG CHOLEEA 

rived from each hyperimmune hog may be appropriately 
mixed with serum from other hyperimmune hogs imme- 
diately after collection, provided the final batch or mix- 
ture is prepared as prescribed in the following para- 
graphs of this section. 

Paragraph 10. Heating of anti-hog-cholera serum 
shall be conducted under the supervision of a bureau 
employee and in a manner in which the product and the 
entire container thereof will be subjected to a tempera- 
ture ranging from 59° to 60° C. for 30 minutes. 

Paragraph 11. Anti-hog-cholera serum which has 
been heated as provided in the preceding paragraph 
shall not be handled thereafter in a manner which will 
expose the product to contamination. Final mixtures or 
batches of anti-hog-cholera serum shall contain relative 
proportions of the several bleedings. Single bleedings 
from each hog shall not be divided or become a part of 
two or more batches unless the serum is subjected to 
heat as described in paragraph 10 of this section. 

Paragraph 12. Anti-hog-cholera serum which is to 
constitute a batch or portion thereof may be strained 
into a single container, after which the amount should 
be accurately determined. 

Paragraph 13. Anti-hog-cholera serum shall have 
added thereto a sufficient quantity of a 5 per cent solu- 
tion of phenol to make the serum contain one-half of 1 
per cent of phenol by volume. 

Paragraph 14. Phenolization of anti-hog-cholera se- 
rum must be accomplished with accuracy, and in a man- 
ner which will prevent the occurrence of undesirable 
changes in the product. 

Paragraph 15. All records shall indicate clearly the 
particular hog or group of hogs from which each batch 
of serum or portion thereof is derived. The amount 
prepared for phenolization and the total amount after 
phenolization shall be separately recorded. 



APPENDIX 285 

Section 3. Paragraph 1. Anti-hog-cholera serum 
prior to testing shall be collected in batches of not more 
than 100,000 cubic centimeters each, which shall be 
thoroughly mixed in a single container. After mixing 
and phenolizing, a representative sample consisting of 
at least 375 cubic centimeters collected in three contain- 
ers of not less than 25 centimeters, each to be known as 
the '^Serum-test sample," shall be taken and marked 
with identifying marks by a bureau employee. The se- 
rum, together with the test sample, shall be placed under 
bureau lock, as provided under (b) section 1, Regula- 
tion 7, and so held until such time as the tests required 
by these regulations have been completed, and have 
shown that the serum is not worthless, contaminated, 
dangerous, or harmful. 

Paragraph 2. If the serum is released, one of the 
three containers of the test sample thereof shall be held 
under bureau lock for at least six months after the latest 
return date shown on the trade labels affixed to the im- 
mediate or true containers of the serum of which the test 
sample is a part. 

Section 4. Paragraph 1. All anti-hog-cholera serum 
shall be tested for purity and potency by licensed estab- 
lishments as prescribed by these regulations. 

Paragraph 2. For use in testing each batch of 100,- 
000 cubic centimeters of anti-hog-cholera serum of less, 
7 healthy pigs, susceptible to hog cholera and weighing 
not less than 45 pounds and not more than 90 pounds 
each, shall be furnished by the establishment. 

Paragraph 3. Each of the seven pigs furnished for 
the test shall be injected with 2 cubic centimeters of 
hog-cholera virus; of these pigs 5 shall receive 20 cubic 
centimeters of the serum Avhich is to be tested. Two of 
the pigs shall receive no serum and shall serve as con- 
trols. The virus and serum injections shall be made 
simultaneously, the virus being injected into the left and 



286 HOG CHOLEEA 

the serum into tlie right axillary space. The same vims 
shall be used for the inoculation of all pigs in the test 
and shall be administered by a veterinary inspector. 

Paragraph 4. A veterinary inspector shall indicate 
the pigs which shall receive serum with virus and those 
which shall receive the virus only in each serum test. 

Paragraph 5. Pigs which are injected with serum in 
serum tests shall be held under the observation of a 
veterinary inspector for a period of 21 days, or as much 
longer as the inspector in charge may deem necessary 
to determine the health of the animals and the purity 
and potency of the serum under test. 

Paragraph 6. Pigs in serum tests which receive virus 
only shall be held under the observation of a veterinary 
inspector and shall not be removed from the test unless 
and until released by such an inspector who will permit 
their removal when exhibiting well-marked symptoms of 
hog cholera, as described in rule D, paragraph 2, sec- 
tion 5, of this regulation, or after they have served their 
purpose in the tests. 

Paragraph 7. The temperature of each pig used in a 
test of anti-hog-cholera serum shall be taken and re- 
corded shortly before each test is inaugurated. 

Paragraph 8. Temperatures of control pigs and sick 
serum-treated pigs in serum tests shall be procured daily 
throughout the test period, with the possible exception of 
Sundays and holidays, and an accurate report of these 
temperatures rendered by the establishment to the in- 
spector in charge as he may direct. 

Paragraph 9. When serum-treated pigs do not ex- 
hibit symptoms of sickness their temperatures need not 
be taken except when required by the inspector in charge 
or his assistants to determine more accurately the true 
physical condition of the animals under observation. 

Section 5. Paragraph 1. The following principle 



APPENDIX 287 

and rules are declared for a guide in judging the re- 
sults of serum tests : 

Principle : It is practically impossible in many cases 
accurately to differentiate between hog cholera, pneu- 
monia, and other conditions affecting hogs, without the 
aid of an autopsy as well as applied laboratory technique 
and certain experiments which may be necessary to de- 
termine the causative agent responsible for the condi- 
tion. Therefore, when healthy pigs are selected for test- 
ing- anti-hog-cholera serum any abnormal condition 
which may arise in the pigs subsequent to their inocula- 
tion should be regarded as due either to the virus used 
or, in the case of the serum-treated pigs, to the fact that 
the serum does not protect, unless the condition is defi- 
nitely known or can be shown to be due to some other 
cause. 

Paragraph 2. The following rules shall be observed in 
disposing of anti-hog-cholera serum which has been sub- 
jected to the tests prescribed by this order: 

Rule A. A serum test shall be declared a *'No test"" 
if any one of the following conditions obtains : 

1. When any of the serum-treated test pigs or both of 
the control pigs become visibly sick on or before the 
fourth day after the time of inoculation. 

2. When both of the control pigs do not exhibit symp- 
toms of hog cholera at some time during the test period 
as described in rule D of this paragraph. 

3. When neither of the control pigs exhibits symp- 
toms of hog cholera subsequent to the fourth day and 
within 7 days after the time of inoculation as described 
in rule D of this paragraph. 

4. When one or both of the control pigs exhibit sj^mp- 
toms of hog cholera within 7 days, as prescribed in rule 
D of this paragraph, but do not become sick to a degree 
sufficient to result in death within 15 days after the 
time of inoculation. 



288 HOG CHOLERA 

5. Wlien the senim-treated test pigs develop during 
the test period symptoms of any infections, contagions, 
or communicable disease (other than hog cholera) which 
is not caused by the serum used. 

6. When a condition obtains in any of the test pigs 
which is not otherwise covered in this section. 

Rule B. A serum test shall be declared "unsatisfac- 
tory and the serum contaminated" when the following 
condition obtains: 

1. When during the test period any of the serum- 
treated test pigs develop symptoms of any infectious, 
contagious, or communicable disease (other than hog 
cholera) which is due to the serum used. 

Rule C. A serum test shall be declared "Unsatisfac- 
tory" when any one of the following conditions obtains: 

1. When both of the control pigs react as described in 
rule D of this paragraph and one of the serum-treated 
pigs becomes visibly sick subsequent to the fourth day 
after the time of inoculation and is found not to have 
fully recovered before the test animals are released by a 
veterinary inspector, as provided in paragraph 5, section 
4, of this regulation. 

2. When both of the control pigs react as described in 
rule D and two or more of the serum-treated pigs be- 
come visibly sick after the fourth day after the time of 
inoculation. 

3. When an abscess, which is not definitely known to 
be due to a cause other than the serum used, develops at 
the site of the serum inoculations in any of the serum- 
treated pigs. 

Rule D. A serum test shall be declared "Satisfac- 
tory" when the following conditions obtain: 

1. When both of the control pigs exhibit visible symp- 
toms of hog cholera at some time during the test period, 
one of which becomes visibly sick of this disease subse- 
quent to the fourth day of this period but within seven 



APPENDIX 289 

days after the test is inaugurated, and is sick to a de- 
gree sufficient to result in death within 15 days after the 
time of inoculation, while all of the serum-treated pigs 
remain well throughout the test or not more than one 
of these serum-treated pigs become visibly sick subse- 
qu.ent to the fourth day after the time of inoculation, 
and fully recovers before the test animals are released 
by a veterinary inspector as provided in paragraph 5 
section 4, of this regulation. 

Section 6. Paragraph 1. Anti-hog-cholera serum 
may be released for marketing as hereinafter prescribed 
when the test required by this regulation is found to be 
satisfactory as defined in rule D, provided the product 
is recommended for use in doses not less than those ap- 
pearing in the following table. This table shall be a 
part of trade labels, wrappers, and the like, affixed to or 
used in connection v/ith each immediate or true con- 
tainer of the product. 

We ig h t . Minimum D ose. 

Sucking pigs 20 c. c. 

Pigs 20 to 40 pounds 30 c. c. 

Pigs 40 to 90 pounds 35 c. c. 

Pigs 90 to 120 pounds 45 c. c. 

Hogs 120 to 150 pounds 55 c. c. 

Hogs 150 to 180 pounds 65 c. c 

Hogs 180 pounds and over 75 c. c. 

Paragraph 2. Anti-hog-cholera serum, the test of 
which has proved it to be "Unsatisfactory," as defined 
in rule C of this order, may be tested again as described 
in sections 4 and 5 of this regulation. Should the sec- 
ond test prove to be " Satisfactor}^ " as defined in rule 
D, the serum may be released for marketing under the 
conditions set forth in paragraph 1 of this section. If 
the test is again found "Unsatisfactory," as defined in 
1 and 2, rule C, paragraph 2, section 5, of this regula- 
tion, the serum shall not be marketed unless and until 



290 HOG CHOLEKA 

it is either concentrated, refined and tested in a manner 
approved by the chief of bureau, or mixed with other 
serum and tested as provided in section 7 of this regu- 
lation. 

Section 7. ParagrapJi 1. "When it is desired to mar- 
ket anti-hog-cholera serum without concentration and re- 
finement which has been tested with the results indi- 
cated in paragraph 2, section 6, of this regulation, it 
shall be mixed with other anti-hog-eholera serum with 
the view of increasing its potency and the final mixture 
shall consist of not less than 50 per cent nor more than 
60 per cent of the serum of doubtful potency. 

Paragraph 2. Anti-hog-cholera serum which has been 
mixed as provided in the preceding paragraph shall be 
tested as outlined in sections 4 and 5 of this regulation, 
with the following exceptions: 

{a) Eleven pigs in lieu of the 7 shall be used, 3 of 
which shall receive virus only and shall serve as controls. 

(&) Unless two of the control pigs exhibit visible 
symptoms of hog cholera subsequent to the fourth day 
of the test period, but within 7 days after the test is 
inaugurated and are sick of this disease to a degree suffi- 
cient to result in death within 15 days after the time 
of inoculation, ''No test" will be declared. 

Paragraph 3. A second test conducted in the same 
manner as before may be made of serum mixed as pro- 
vided in paragraph 1 of this section should the results of 
the test of the mixture be declared ''Unsatisfactory" as 
to potency. 

Section 8. Paragraph 1. Should abscesses develop 
at the sites of the serum inoculations in any of the pigs 
used for testing serum as provided in this regulation, 
the following rules shall apply : 

{a) Judgment of the results of tests made on pigs to 
determine the potency of anti-hog-cholera serum will be 



APPENDIX 291 

rendered irrespective of those conditions found which 
are regarded as an index to the purity of the product. 

(h) Should the results of a test of an ti -hog-cholera 
serum be declared "Satisfactory for purity," and it is 
found necessary to subject the batch of serum to a re- 
test to determine its potency, judgment concerning 
the purity of the product shall be based upon the 
first test unless evidence is found subsequent to such 
test which indicates that the serum is in fact contami- 
nated. 

(c) Should the results of a test of anti-hog-cholera 
serum be declared ' ' Satisfactory for potency ' ' but ^ ' Un- 
satisfactory for purity" the product may again be tested 
for purity upon the same number of pigs as provided 
under (a), paragraph 2, section 7, of this regulation 
provided each pig receives a single injection, in the 
axillary space, of at least 25 cubic centimeters of the 
product to be tested. Immune pigs may be used for this 
test if desired, and they shall be held under the super- 
vision of a bureau employee for at least 15 days. 

Paragraph 2. Anti-hog-cholera serum may be released 
for marketing as prescribed in paragraph 1, section 6, 
of this regulation, after having been tested, as provided 
by sections 7 and 8 and found satisfactory for purity 
and potency. 

Section 9. Paragraph 1. Anti-hog-cholera serum 
which has been tested twice with unsatisfactory results 
as to purity as provided in 3 of rule C of this regulation 
but satisfactory as to potency may again be tested with 
the view of ascertaining whether it is in fact contami- 
nated with pus-producing organisms, by treating 50 
hogs on the premises of the manufacturing establish- 
ment. The serum shall be administered under the super- 
vision of a bureau employee, and each hog treated shall 
receive a single injection, in the axillary space, of not 



292 HOG CHOLERA 

less than 25 cubic centimeters of the product to be 
tested. 

Paragraph 2. Animals used for testing serum as pre- 
scribed in paragraph 1 of this section shall be held under 
the supervision of a bureau employee for at least 15 
days, and each animal carefully examined at the sites 
of the inoculations to determine whether or not the 
product has caused abscess formation. At the conclu- 
sion of the test a report shall be submitted to the Wash- 
ington office by letter concerning the results thereof, 
after which the bureau will advise the inspector in 
charge as to what disposition should be made of the 
serum. 

Section 10. Paragraph 1. Blood derived from hyper- 
immune hogs and ordinary defibrinated blood anti-hog- 
eholera serum may be clarified, or refined and concen- 
trated by licensed establishments, provided methods used 
to accomplish this are approved by the chief of bureau. 

Paragraph 2. When products described in the pre- 
ceding paragraph which have not been tested or have 
been tested and found '' Satisfactory" are clarified, or 
refined and concentrated so that the volume thereof is 
reduced 20 per cent or more, and it is desired to market 
the produ.ct in doses smaller than those indicated in 
paragraph 1, section 6 of this regulation, it shall be 
tested as provided in sections 4 and 5 of this regulation, 
except that each pig in the test shall receive 15 cubic 
centimeters of the product to be tested. 

Paragraph 3. Should the test required in paragraph 
2 of this section be found "Satisfactory," as provided 
in rule D, paragraph 2, section 5 of this regulation, the 
product may be marketed, if it is recommended for use 
in doses not less than those appearing in the following 
table. This table shall be a part of trade labels, wrap- 
pers, and the like, affixed to or used in connection with 
each immediate or true container of the product : 



APPENDIX 293 

Weight. Minimum Dose. 

Sacking pigs 15 c. c. 

Pigs 20 to 40 pounds 25 c. c. 

Pigs 40 to 90 pounds 30 e. c. 

Pigs 90 to 120 pounds 35 c. c. 

Hogs 120 to 150 pounds 45 c. c. 

Hogs 150 to 180 pounds 50 c. c. 

Hogs 180 pounds and over 60 c. c. 

Section 11. Paragraph 1. Each immediate or true 
container of anti-hog-cholera serum which has been 
tested and found not to be worthless, contaminated, dan- 
gerous, or harmful shall bear a stamp or mark approved 
by this department. Such stamp or mark shall bear the 
phrase ''U. S. Released." Each container of anti-hog- 
cholera serum shall be appropriately sealed with a suit- 
able material and the aforesaid stamp or mark shall be 
affixed securely to the sealing material under the super- 
vision of a bureau employee. Should any difficulty re- 
sult from the action of moisture upon said stamp or 
mark causing it to become detached or illegible, that por- 
tion of the container which has been sealed and stamped 
shall be subjected at once to dipping in hot paraffin or 
other waterproof material. 

Paragraph 2. The return date placed upon trade 
labels of anti-hog-cholera serum shall be a date not more 
than two years after the date of bleeding. The date of 
bleeding shall be regarded as the date upon which the 
first serum was collected, which is a part of the batch. 

Paragraph 3. Should the return date of any batch 
of anti-hog-cholera serum which has been tested as pro- 
vided in this regulation expire before the serum is used, 
this date may be extended one year, provided the serum 
is retested and found satisfactory as defined in rule D, 
paragraph 2, section 5, of this regulation. 

Paragraph 4. Trade labels affixed to or used in con- 
nection with the immediate or true containers of anti- 



294 HOG CHOLERA 

hog'-cholera serum shall plainly show the quantity of 
the contents of said containers. 

Paragraph 5. No immediate or true container of anti- 
hog-cholera serum shall be filled in whole or in part, and 
no trade label shall be affixed to such containers, except 
under the supervision of a bureau employee. 

Paragraph 6. Anti-hog-cholera serum shall not be 
removed from the premises of a licensed establishment 
unless it has been prepared in accordance with the pro- 
visions of these regulations. 

Paragraph 7. No anti-hog-cholera serum shall be re- 
leased for marketing unless and until all of the informa- 
tion required by those regulations has been affixed to 
the containers thereof under the supervision of a bureau 
employee. 

Section 12. The following special facilities and such 
others as may be required by the chief of bureau shall 
be provided by each establishment licensed to prepare 
anti-hog-cholera serum. 

(a) Separate operating rooms. 

(&) A separate room in which the hogs shall be 
washed, cleaned, and otherwise prepared before being 
taken into the operating room. 

(c) A separate room for conducting autopsies. 

{d) A separate room for the preparation and mixing 
of serum. 

(e) A separate room for washing and sterilizing 
equipment. 

(/) Clean cloths, which shall be kept damp when in 
use, to be used for covering hogs during all operations 
incident to the collection of anti-hog-cholera serum. 

ig) All outside doors, windows, or other openings 
shall be equipped with dust screens. 

Section 13. All persons immediately before entering 
the operating or laboratory rooms of an establishment, 
licensed to prepare anti-hog-cholera serum, shall change 



APPENDIX 295 

their outer clothing or effectively cover the same by the 
use of gowns or other satisfactory garments. 



REGULATION 20. — BACTERINS, VACCINES, TOXINS, ETC. 

Section 1. Paragraph 1. Viruses entering into the 
preparation of bacterins, vaccines, or toxins shall be de- 
rived from animals which are affected with no disease 
other than that for which the bacterins, vaccines, or 
toxins are intended to be used. 

Paragraph 2. All bacterins, vaccines, and toxins, shall 
be derived from the specific cause of the diseases for 
which they are intended to be used, or from the secon- 
dary invaders of the respective diseases. 

Section 2. Paragraph 1. The return date on the 
trade labels of blackleg vaccine prepared from attenu- 
ated B. gangrcenoi emphysematosoi or blackleg muscle 
virus, shall be a date not more than 6 months later than 
the date on which the preparation of the product is 
completed, without regard to the filling of final con- 
tainers. 

Paragraph 2. The return date on the trade labels of 
anthrax vaccine prepared by the Pasteur method shall be 
a date not more than 3 months later than that on which 
the preparation of the product is completed without 
regard to the filling of final containers. 

Section 3. The immunity unit for measuring the 
strength of tetanus antitoxin shall be 10 times the least 
quantity of antitetanic serum necessary to save the life 
of a 350-gram guinea pig for 96 hours against the official- 
test dose of the standard toxin furnished by the Hy- 
gienic Laboratory of the United States Public Health 
Service. The number of the immunity units recom- 
mended for the prevention of tetanus in a horse shall 
be at least 500 units. 



296 HOG CHOLERA 

REGULATION 21. ADMISSION OF VIRUSES, SERUMS, TOXINS, 

AND ANALOGOUS PRODUCTS 

Section 1. No virus, serum, toxin, or analogous prod- 
uct which has not been prepared, handled, stored, and 
marketed in accordance with these regulations, and no 
virus, serum, toxin, or analogous product which is worth- 
less, contaminated, dangerous, or harmful shall be 
brought on to the premises of any licensed establish- 
ment. 

THE virus-serum-toxin LAW 

[Extract from "An act making appropriations for the Depart- 
ment of Agriculture for the fiscal year ending June 30, 1914," 
approved March 4, 1913 (37 Stat., 832).] 

That from and after July first, nineteen hundred and 
thirteen, it shall be unlawful for any person, firm, or 
corporation to prepare, sell, barter, or exchange in the 
District of Columbia, or in the Territories, or in any 
place under the jurisdiction of the United States, or to 
ship or deliver for shipment from one State or Territory 
or the District of Columbia to any other State or Terri- 
tory or the District of Columbia, any worthless, contami- 
nated, dangerous, or harmful virus, serum, toxin, or 
analogous product intended for use in the treatment of 
domestic animals, and no person, firm, or corporation 
shall prepare, sell, barter, exchange, or ship as aforesaid 
any virus, serum, toxin, or analogous product manufac- 
tured within the United States and intended for use in 
the treatment of domestic animals, unless and until the 
said virus, serum, toxin, or analogous product shall have 
been prepared, under and in compliance with regula- 
tions prescribed by the Secretary of Agriculture, at an 
establishment -holding an unsuspended and unrevoked 
license issued by the Secretary of Agriculture as herein- 
after authorized. That the importation into the United 
States, without a permit from the Secretary of Agricul- 



1 



APPENDIX 297 

ture, of any virus, serum, toxin, or analogous product 
for use in the treatment of domestic animals, and the 
importation of any worthless, contaminated, dangerous, 
or harmful virus, serum, toxin, or analogous product for 
use in the treatment of domestic animals, are hereby 
prohibited. The Secretary of Agriculture is hereby au- 
thorized to cause the Bureau of Animal Industry to ex- 
amine and inspect all viruses, serums, toxins, and analo- 
gous products, for use in the treatment of domestic ani- 
mals, which are being imported or offered for importa- 
tion into the United States, to determine whether such 
viruses, serums, toxins, and analogous products are 
worthless, contaminated, dangerous, or harmful, and if 
it shall appear that any such virus, serum, toxin, or 
analogous product, for use in the treatment of domestic 
animals, is worthless, contaminated, dangerous, or harm- 
ful, the same shall be denied entry and shall be destroyed 
or returned at the expense of the owner or importer. 
That the Secretary of Agriculture be, and hereby is, 
authorized to make and promulgate from time to time 
such rules and regulations as may be necessary to pre- 
vent the preparation, sale, barter, exchange, or shipment 
as aforesaid of any worthless, contaminated, dangerous, 
or harmful virus, serum, toxin, or analogous product for 
use in the treatment of domestic animals, and to issue, 
suspend, and revoke licenses for the maintenance of es- 
tablishments for the preparation of viruses, serums, tox- 
ins, and analogous products, for use in the treatment of 
domestic animals, intended for sale, barter, exchange, or 
shinment as aforesaid. The Secretary of Agriculture is 
hereby authorized to issue permits for the importation 
into the United States of viruses, serums, toxins, and 
analogous products, for use in the treatment of domestic 
animals, which are not worthless, contaminated, danger- 
ous, or harmful. All licenses issued under authority of 
this Act to establishments where such viruses, serums, 
toxins, or analogous products are prepared for sale, bar- 
ter, exchange, or shipment as aforesaid, shall be issued 
on condition that the licensee shall permit the inspection 
of such establishments and of such products and their 



298 HOG CHOLERA 

preparation ; and the Secretary of Agriculture may sus- 
pend or revoke any permit or license issued under au- 
thority of this Act, after opportunity for hearing has 
been granted the licensee or importer, when the Secre- 
tary of Agriculture is satisfied that such license or per- 
mit is being used to facilitate or effect the preparation, 
sale, barter, exchange, or shipment as aforesaid, or the 
importation into the United States of any worthless, 
contaminated, dangerous, or harmful virus, serum, toxin, 
or analogous product for use in the treatment of domes- 
tic animals. That any officer, agent, or employee of the 
Department of Agriculture duly authorized by the Sec- 
retary of Agriculture for the purpose may, at any hour 
during the daytime or nighttime, enter and inspect any 
establishment licensed under this Act where any virus, 
serum, toxin, or analogous product for use in the treat- 
ment of domestic animals is prepared for sale, barter, 
exchange, or shipment as aforesaid. That any person, 
firm, or corporation who shall violate any of the provi- 
sions of this Act shall be deemed guilty of a misde- 
meanor, and shall, upon conviction, be punished by a 
fine of not exceeding $1,000 or by imprisonment not ex- 
ceeding one year, or by both such fine and imprisonment, 
in the discretion of the court. 



UNITED STATES DEPARTMENT OF AGRICUL- 
TURE, BUREAU OF ANIMAL INDUSTRY 

Amendment 1 to B. A. I. Order 265 

Regulations Governing the Preparation, Sale, Barter, 
Exchange, Shipment, and Importation of Viruses, 
Serums, Toxins, and Analogous Products Intended 
for Use in the Treatment of Domestic Animals. 

Effective on and after August 1, 1920 

U. S. Department of Agriculture, 

Office of the Secretary, 
Washington^ D. C, July 14, 1920. 
Under authority conferred by law upon the Secretary 
of Agriculture, paragraph 2, section 3, Regulation 17 of 
B. A. I. Order 265, dated August 1, 1919, and effective 
September 1, 1919, is hereby revoked. 

Section 9, Regulation 17, is amended by adding thereto 
a paragraph, numbered paragraph 5, reading as herein- 
after set forth. 

Paragraphs 2 and 3, section 5, Regulation 2 ; paragraph 
7, section 2, Regulation 12 ; paragraph 1, section 3, para- 
graph 2, section 4, (&) paragraph 3, and {a) and (&) 
paragraph 4, section 9, Regulation 17 ; paragraph 5, sec- 
tion 5, Regulation 18; paragraph 2, section 6, (c) para- 
graph 1, section 8, and paragraph 3, section 11, Regula- 
tion 19 ; and paragraph 1, section 2, Regulation 20 of 
B. A. I. Order 265, are hereby amended so as to read as 
hereinafter set forth. 

This amendment, for the purpose of identification, is 
designated Amendment 1 to B. A. I. Order 265, and shall 
become and be effective on and after August 1, 1920. 

E. D. Ball, 
Acting Secretary of Agriculture, 
299 



300 HOG CHOLERA 

REGULATION 2. ^LICENSES AND INSPECTIONS 

Section 5. Paragraph 2. Licenses shall be numbered 
and shall be in the following form : 

United States Veterinary License No 

Washington, D. C, 

This is to certify that, pursuant to the terms of the act 
of Congress approved March 4, 1913 (37 Stat., 832), 
governing the preparation, sale, barter, exchange ship- 
ment, and importation of viruses, serums, toxins, and 
analogous products intended for use in the treatment of 

domestic animals, is 

hereby licensed to maintain at 

an establishment for the preparation or : 

This license is subject to termination as provided in 
the regulations made under the authority contained in 
said act approved March 4, 1913, and also to suspension 
or revocation if the licensee violates or fails to comply 
with any provision of the said act or the regulations 
made thereunder. 



Secretary of Agriculture. 
Countersigned : 



Chiefs Bureau of Animal Industry. 

Section 5. Paragraph 3. Should a licensed establish- 
ment discontinue the production of any virus, serum, 
toxin, or analogous product, the license of such establish- 
ment shall be returned to the bureau for termination and 
a new license issued covering such products named 
therein as the establishment shall continue to produce. 
Should an establishment be engaged in the preparation 
of various products under a number of licenses issued 
from time to time by the department, the licenses shall 
be returned to the bureau at its request for termination 
and a new license issued covering all of the products 



i 



APPENDIX 301 

embraced in the returned licenses which the establish- 
ment shall continue to produce. 

REGULATION 12. — LABELS 

Section 2. Paragraph 7. The name and address of 
the manufacturer may be omitted from trade labels 
when any virus, serum, toxin, or analogous product is 
to be distributed by a person other than the manufac- 
turer, but in such case the distributor must state on the 
label his or its trade name and address in immediate 
connection with a statement showing the license under 
which the product was manufactured. This statement, 
together with the name and address of the distributor, 
shall appear in letters of uniform size and character 
and be in the following form: "Produced under U. S. 

Veterinary License No. . Distributed by (name 

and address of distributor)." The name of the dis- 
tributor shall not appear on the label except in imme- 
diate connection with the Federal license legend. 

REGULATION 17. — ANIMALS 

Section 3. Paragraph 1. All hogs which are admit- 
ted to the premises of licensed establishments under the 
provisions of section 1, paragraph 1, of this regulation 
shall be held in receiving pens for at least 24 hours after 
admission to the premises, and during this time they 
shall be allowed free range and contact with not less 
than 2 contact calves for each lot of 200 hogs or less in 
the receiving pens. 

Section 4. Paragraph 2. The removal of contact 
calves from receiving pens shall be so arranged that a 
rotation will be established whereby each animal will 
be replaced at intervals of one month and both animals 
replaced every two months. 

Section 9. Paragraph 3 (&). Hogs which survive 
inoculation and exposure for the production of hog- 



302 HOG CHOLERA 

cholera virus, surviving controls from tests of anti-hog- 
cholera serum, and surviving hogs which have been used 
for testing hog-cholera virus may be removed from the 
premises of the establishment not sooner than 15 days 
subsequent to the day of inoculation and exposure, pro- 
vided they are healthy. It is required, however, that all 
such hogs before their removal from the premises be 
given the serum-alone treatment as prescribed under 
(a) of paragTaph 4 of this section, or the simultaneous 
treatment prescribed under (h) of the same paragraph 
and section. Hyperimmune hogs and pigs used for test- 
ing the purity and potency of anti-hog-cholera serum 
may be removed from the premises of licensed establish- 
ments 21 days subsequent to the day of hyperimmuniza- 
tion or inoculation, provided they exhibit no symptoms 
of any infectious, contagious, or communicable disease, 
and provided further that they are first disinfected as 
prescribed in paragraph 5 of this section. Other hogs 
shall be removed from the premises of the establishment 
only after treatment and disinfection as provided in 
paragraph 5 of this section, except that such hogs need 
not be held 21 days when treated with serum and virus 
which have been released for marketing. 

Section 9. Paragraph 4 (a) . Serum-alone method. — 
The serum used shall have been prepared and released 
for marketing at an establishment holding a license from 
the Secretary of Agriculture and the dose employed 
shall conform to that required in paragraph 1, section 6, 
or paragraph 3, section 10, of Regulation 19. After 
receiving this treatment they shall be disinfected as pre- 
scribed in paragraph 5 of this section. 

Section 9. Paragraph 4 (h). Simultaneous-inocula- 
tion method. — The serum and virus used shall have been 
prepared at an establishment holding a license from the 
Secretary of Agriculture and the doses shall be not less 
than those required in paragraph 1, section 6, or para- 



APPENDIX 303 

graph 3, section 10, of Kegnlation 19. After receiving 
this treatment they shall be held under the supervision 
of a bureau employee for a period of at least 21 days, 
except when treated with virus and serum released for 
marketing. If no symptoms of hog cholera or other in- 
fectious, contagious, or communicable disease are ex- 
hibited by the animals, they shall be disinfected as pre- 
scribed in paragraph 5 of this section. 

Section 9. Paragraph 5. Before removal from the 
premises of licensed establishments all hogs shall be dis- 
infected in a 2 per cent aqueous solution of cresol com- 
pound, U. S. P., or a permitted substitute therefor, and 
held in noninfectious pens for a period of at least three 
hours before being loaded for transportation. When 
the temperature of the air is below freezing, comfort- 
able quarters shall be furnished for the disinfected ani- 
mals until they are dry. 

REGULATION 18. — HOG- CHOLERA VIRUS 

Section 5. Paragraph 5. Trade labels affixed to or 
used in connection with each in^iediate or true con- 
tainer of simultaneous virus shall bear a dosage table 
in which the doses recommended are not less than those 
appearing in the following table: 

Weight. Minimum Dose. 

Pigs weighing 45 pounds or less 1 c. c. 

Hogs weighing more than 45 pounds .... 2 c. c. 

regulation 19. — ANTI-HOG-CHOLERA SERUM 

Section 6. Paragraph 2. Anti-hog-cholera serum the 
test of which has proved it to be ''unsatisfactory," as 
defined in 1 and 2 of rule C of this regulation, may be 
tested again as described in sections 4 and 5 of this 
regulation. Should the second test prove to be ''satis- 
factory, ' ' as defined in rule D, the serum may be released 



304 HOG CHOLERA 

for marketing under the conditions set forth in para- 
graph 1 of this section. If the test is again found * * un- 
satisfactory, " as defined in 1 and 2, rule C, paragraph 
2, section 5, of this regulation, the serum shall not be 
marketed unless and until it is either concentrated, re- 
fined, and tested in a manner approved by the chief of 
bureau, or mixed with other serum and tested as pro- 
vided in section 7 of this regulation. 

Sections. FaragrapK 1 {c). Anti-hog-cholera serum 
which has been found ''unsatisfactory for purity" may 
again be tested for purity upon 8 pigs, provided each 
pig receives a single injection in the axillary space of at 
least 20 c. c. of the product to be tested. Immune pigs 
may be used for testing the purity of anti-hog-cholera 
serum if desired. The pigs used should be held under 
the supervision of a bureau employee for at least 15 
days. 

Section 11. Paragraph 3. Should the return date of 
any batch of anti-hog-cholera serum expire before the 
serum is used, the serum should be retested, and if found 
satisfactory as defined in rule D, paragraph 2, section 5, 
of this regulation, tl^^ return date may be extended one 
year from the date of retest. ^ 

REGULATION 20. — BACTERINS, VACCINES, TOXINS, ETC. 

Section 2. Paragraph 1. The return date on the 
trade labels of blackleg vaccine prepared from attenu- 
ated B. chauveaui, or blackleg muscle virus, shall be a 
date not more than one and one-half years later than 
the date on which the preparation of the product is 
completed, without regard to the filling of final con- 
tainers. 



UNITED STATES DEPARTMENT OF AGRICUL- 
TURE, BUREAU OP ANIMAL INDUSTRY 

Amendment 2 to B. A. I. Order 265 

Regulations Governing the Preparation, Sale, Barter, 
Exchange, Shipment, and Importation of Viruses, 
Serums, Toxins, and Analogous Products Intended 
for Use in the Treatment of Domestic Animals. 

U. S. Department of Agriculture, 

Office of the Secretary, 
Washington, D. C, February 15, 1921. 
Under authority conferred by law upon the Secretary 
of Agriculture, paragraphs 1 and 6, section 2, Regula- 
tion 12, of B. A. I. Order 265, dated August 1, 1919, and 
effective September 1, 1919, are hereby amended to read 
as hereinafter set forth. 

Paragraph 7, section 2, Regulation 12, of Amendment 
1 to the above order, dated July 14, 1920, and effective 
on and after August 1, 1920, is hereby revoked ; said rev- 
ocation, as applied to anti-hog-cholera serum and hog- 
cholera virus, to be effective on and after May 1, 1921 ; 
as to other products said revocation to be effective on and 
after January 1, 1922. Paragraph 8, section 2, Regula- 
tion 12, of B. A. I. Order 265 will accordingly, on and 
after January 1, 1922, be designated paragraph 7. 

Paragraph 1, section 3, Regulation 17, of Amendment 
1 of the above order, is hereby amended to read as here- 
inafter set forth. 

This amendment, for the purpose of identification, is 
designated Amendment 2 of B. A. I. Order 265, and 
shall become and be effective on and after March 1, 1921, 
except as provided below. 

E. T. Meredith, 
Secretary of Agriculture. 
305 



306. HOG CHOLERA 

REGULATION 12. LABELS 

Section 2. Paragraph 1. Trade labels shall bear the 
true name of the product contained in the package, and 
this name shall be identical with that given in the license 
under which the product is prepared. The name shall 
also be so lettered and placed as to give equal promi- 
nence to each word composing it. Such labels shall also 
bear the name and address of the manufacturer, and the 
license or permit number assigned by the department. 
The license number and permit number shall be shown 
in either of the following forms, respectively: "U. S. 

Veterinary License No. ," or "U. S. Vet. License 

No. ," and ''U. S. Veterinary Permit No. ," or 

''U. S. Vet. Permit No. ." These labels shall bear 

all other information required by the chief of the bureau, 
and may also bear any other statement not false or mis- 
leading, and which has been approved by the bureau. 

Section 2. Paragraph 6. When any virus, serum, 
toxin, or analogous product is prepared by a licensed 
establishment, or imported for a person other than the 
one to whom a license or permit has been issued, and the 
name and address of the distributor, as well as that of 
the manufacturer, is to appear on the trade labels of the 
containers thereof, a statement shall be made on the 
labels indicating that the virus, serum, toxin, or analo- 
gous product is distributed by such person. The name 
and address of this person shall not appear in any form 
or manner indicating that the distributor is the pro- 
ducer of the product, and operating under the license as 
shown on the label. The terms ''Distributor/' ''Dis- 
tributors," "Distributed by," or equivalent terms may 
be used if prominently placed and lettered, in connec- 
tion with the name and address of the distributing per- 
son, provided the same are not used so as to be either 
false or misleading. Eeference to the distributing per- 
son shall be made by name and address only. 



APPENDIX 307 

The preceding paragraphs 1 and 6, as applied to anti- 
hog-eholera serum and hog-cholera virus, shall become 
and be effective on and after May 1, 1921; as to other 
products they will be effective on and after January 1, 
1922. 

REGULATION 17. — ANIMALS 

Section 3. Paragraph 1. All hogs which are admit- 
ted to the premises of licensed establishments under the 
provisions of section 1, paragraph 1, of this regulation, 
shall be held in receiving pens for at least 24 hours after 
admission to the premises, with the exception of pigs 
which are used in testing the potency and purity of 
anti-hog-cholera serum, in which case 6 hours will be 
sufficient ; and during this time all of these animals shall 
be allowed free range and contact with not less than 
2 contact calves for each lot of 200 hogs or less in the 
receiving pens. 



UNITED STATES DEPARTMENT OF AGRICUL- 
TURE, BUREAU OF ANIMAL INDUSTRY 

Amendment 3 to B. A. I. Order 265 

Reflations Governing the Preparation, Sale, Barter, 
Exchange, Shipment, and Importation of Viruses, 
Serums, Toxins, and Analogous Products Intended 
for. Use in the Treatment of Domestic Animals. 

Effective on and after April 1, 1922 

U. S. Department of Agriculture, 
Office of the Secretary, 
Washington, D. C, March 13, 1922. 
Under authority conferred by law upon the Secretary 
of Agriculture, paragraphs 6, 8, and 9, section 4, Regu- 
lation 18, of B. A. I. Order 265, dated August 1, 1919, 
and effective September 1, 1919, are hereby amended so 
as to provide that three pigs immune to hog cholera may 
be used in lieu of the two calves prescribed by the afore- 
mentioned paragraph 6. 

This amendment, which for the purpose of identifica- 
tion is designated as Amendment 3 to B. A. I. Order 265, 
shall become effective on and after April 1, 1922. 

C. W. PUGSLEY, 

Acting Secretary of Agriculture. 



308 



INDEX 



Abortion, due to simultaneous 
treatment, 146 

Abscesses, following serum 
injection, 135 

Absorption, of injected serum, 
130 

Ante-mortem inspection, in 
outbreaks of hog chol- 
era, 213 

Anthrax, differentiating hog 
cholera from, 71 

Animal inoculation, in diag- 
nosing hog cholera, 67 

Ascarids, as a cause of 
* * serum breaks, ' ' 144 

Ascaris infestation, confused 
with hog cholera, 72 

Autopsy, of virus pig, 87 

Bact. suisepticum, as a com- 
plication of hog chol- 
era, 21, 46, 47, 52 
hemorrhages due to, 53, 56 

Bladder, hog cholera lesions 
in, 53 

Bleeding, for serum, 98 
the virus pig, 85 

B. necrophorus, complicating 
hog cholera, 30, 43, 44, 
45, 47 

B. pyocyaneus, complicating 
hog cholera, 27, 47 

B. pyogenes suis, lesions pro- 
duced in swine, 33 

* ' Breaks, ' ' following serum- 
virus treatment, 18, 
140, 181, 182 

B. suipestifer, ''button ul- 
cers ' ' due to, 45 
complicating hog cholera, 

25, 50, 52 
relation to hog cholera, 3 



Buildings required for serum 
preparation, 78 

Cecum, hog cholera lesions in, 
44 

Confinement, of hogs for 
serum treatment, 118 

Diagnosis, of hog cholera, 58 

Diagnosis, differential, of hog 
cholera, 68 

Disinfectants, as destroyers 
of hog cholera virus, 
12 

Dissemination, of hog chol- 
era, 17 

Dosage, of serum, 131 
of serum and virus, 138 

Dose table, of serum. Bureau 
of Animal Industry, 
110 

Equipment, for serum prepa- 
ration, 80 

Feeder hogs, handling to pre- 
vent hog cholera, 180 
relation to hog cholera dis- 
semination, 236 

[Fees, veterinarian 's, for serum 
administration, 191 

Filterable virus, the cause of 
hog cholera, 4, 8 
disinfectants, destroyers of. 

12 

elimination of, following 

serum-virus treatment, 

147 

heat as a destroyer of, 11 

putrefaction as a destroyer 

of, 11 
virulence of, 10 

"Flu," so-called, differenti- 
ating from hog cholera, 
71 



309 



310 



INDEX 



Follow-up treatment, 153 
Garbage fed swine herds, 
veterinary supervision 
of, 219 
Garbage feeding, as a means 
of hog cholera spread, 
17, 214 
and sanitary considera- 
tions, 225 
licenses for, 227 
municipal, 217, 218 
Heart, hog cholera lesions in, 

47 
Heat, as a destroyer of hog 

cholera virus, 11 
Hemorrhagic septicemia, rela- 
tion to ''serum 
breaks," 149 
History, of outbreak, in rela- 
tion to hog cholera di- 
agnosis, 58, 59 
Hog cholera, complications, 
21 
control and eradication of, 

230 
diagnosis, 58 
diagnosis, differential, 68 
economic importance, 2 
forms of, 35, 36 
handling in the field, 158 
history of, 1 
incubation period of, 35 
infected herd, handling, 161 
lesions of, 40-56 
methods of dissemination, 

17 
nature and cause, 7 
prognosis, 74 
relation to garbage feeding, 

214 
relation to meat inspection, 

197 
symptoms, 35 
Hog holder, 123 
Hyperimmune, the, 89 
Hypering, dangers due to, 95 

technique, 90 
Immunity, of young pigs to 
cholera, 8, 171, 172 
establishing herd, 174 



Immunity, active, due to fol- 
low-up treatment, 155 
active, due to simultaneous 

treatment, 138, 151 
passive, due to serum alone, 
127, 136 

Kidney, hog cholera lesions 
in, 50, 51 

Label, features of serum, 111 
features of virus, 116 

Larynx, hog cholera lesions 
in, 45 

Legislation, regarding use of 
serum and virus, 192, 
193 

Lesions, of hog cholera, 40 
as an aid in diagnosing hog 
cholera, 63 

Lungs, hog cholera lesions in, 
45 

Lung worm infestation, con- 
fused with hog cholera, 
72 

Lymph glands, hog cholera 
lesions in, 54 

Lysol, as a destroyer of hog 
cholera virus, 15 

Marketing hogs, following 
serum and virus treat- 
ment, 169 

Meat inspection, in field out- 
breaks of hog cholera, 
210 
relation of hog cholera to, 
197 

Mixed infection, in swine, 33 

Mortality, due to hog chol- 
era, 7 

Mouth and pharynx, hog 
cholera lesions in, 43 

Putrefaction, as a destroyer 
of hog cholera virus, 
11 

Eeferences, 243 

Eegulations, meat inspection. 
B. A. I. relative to hog 
cholera, 199, 200 
relative to preparation and 
sale of biologies (B. 
A. L), 247 



INDEX 



311 



Einderpest, differentiating 

from hog cholera, 74 
Eouget, differentiating from 

hog cholera, 74 
Septicemia, following serum 

treatment, 134 
Serum, anti-hog-cholera, fees 
for administering, 
191 
keeping qualities, 114 
Serum, anti - hog - cholera, 

methods of using, 118, 
126 
follow-up method, descrip- 
tion, 153 
indications and contrain- 
dications, 157 
serum alone, method, 127 
dangers due to, 133 
indications and contrain- 
dications, 137 
technique of administer- 
ing, 128 
therapeutic value of, 
133 
simultaneous method, 137 
dangers, 139 
dosage of serum and 

virus, 138 
indications and contrain- 
dications, 152 
technique of, 138 
Serum, anti-hog-cholera, or- 
dering, 188 
anti-hog-cholera, prepara- 
tion of, 76 
anti-hog-cholera, testing, 

105 
bleeding for, 98 
bottling and labeling. 111 
B. A. I. Regulations for, 

247 

clear and ''bloody," 112 

principle involved in, 82 

tail and carotid bled, 113 

Serum ' ' breaks, ' ' preventing 

and handling, 145 



Shipping, as a cause of serum 

''breaks," 142, 181, 

182 
Show hogs, handling to pre- 
vent hog cholera, 185 
Site of injection, choice of, 

128 
Small intestine, hog cholera 

lesions in, 44 
Spiroeheta hyos, relation to 

hog cholera, 33 
Spleen, hog cholera lesions in, 

47 
Swine plague, differentiating 

from hog cholera, 70 
in cholera immune herds, 

25 
Stomach, hog cholera lesions 

in, 43 
Stunting, of pigs, as a result 

of simultaneous treat- 
ment, 146 
Symptoms of hog cholera, 35 
as related to diagnosis, 60 
Technique, of serum adminis- 
tration, 128 
Temperature readings, as an 

aid in diagnosis, 61 
Temperatures, low, influence 

on hog cholera virus, 

12 
Trachea, hog cholera lesions 

in, 45 
Tuberculosis, differentiating 

from hog cholera, 71 
' ' Vaccination Cholera, ' ' 18, 

140 
Virus "breaks," 140, 147 
Virus of hog cholera, keeping 

qualities, 116 
labeling, 116 
manner of producing, 84, 

115 
Virus, laboratory, relation to 

hog cholera spread, 18 
Virus pig, the, 84 
autopsy of, 87 



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